Crossfire Protocol Handbook
===========================
Crossfire Development Team <crossfire@metalforge.org>
:numbered:
:toc:

This handbook is the collective result of various authors compiled together
over the course of many years, most of the time after the actual code was
already written (for a long time). As such it will surely contain errors, omit
certain important details, and possibly make life miserable. Nevertheless, any
new developer or curious player should be able to find most of the relevant
information here. If inconsistencies are found or this documentation proves to
be inadequate, consider the latest server-side protocol code in the public
source code repository as the authoritative reference.

Introduction
------------
If you were ever curious enough to `telnet` or `netcat` to a Crossfire server,
chances are you were sorely disappointed. While the protocol may seem to use
plain text at first, it actually uses a mix of ASCII and binary data. This
handbook attempts to document various aspects of the Crossfire protocol.

As always, consult the 'README' file to find out how to get in touch with
helpful people via mailing lists, IRC, and more.

History
~~~~~~~
Originally, the communications plan was set to be a text based system. It
was up to the server and client to parse these messages and determine what
to do. These messages were assumed to be 1 line per message.

At a reasonably early stage of development, Eric Anderson wrote a fairly
(but not totally) complete client/server that used his eutl package. This
package pretty much set up packets with subpackets - these subpackets would
have a tag for the data type, then the data itself. Thus, you could send
many data types, and after transmission, the other end could decode these
commands.

This works fairly well, but I think the creation of numerous sub packets has
some performance hit. Also, the eutl was not especially well documented, so
writing a client for a different platform became more difficult (you needed
to first port over eutl.) An example such of this is the Java client. Also,
Eric left to work on other products shortly after writing his client, which
didn't really leave anyone with a full understanding of the socket code.

I have decided to remove the eutl dependency. At least one advantage is that
having this network related code directly in the client and server makes
error handling a bit easier/cleaner.

Packet Format
~~~~~~~~~~~~~
IMPORTANT: Instead of a straight text method, the outside packet method is:
<size (2 bytes)><data (size bytes)> The <size> is the size of the data
packet, the 2 byte size for the size information is not included here.

Eutl originally used 4 bytes for the size - to me, 2 bytes seems plenty
(gives a maximum packet of 32767 - I can't see ever going beyond a few
thousand, simply because in a fast action game, transmission size of such a
packet would probably not make things playable.) While saving 2 bytes might
not be much, it makes a least some sense.

The actual data is something of the nature of the commands listed below. It
is a text command, followed by possible other data. The remaining data can
be binary - it is up to the client and server to decode what it sent.

The commands as described below is just the data portion of the packet. If
writing a new client, remember that you must take into account the size of
the packet. There is no termination of packets, other than knowing how long
it should be.

For now, most everything that is sent is text. This is more or less how
things worked under eutl, except it packed the ints into 4 bytes in a known
order. In some cases, we handle ints as strings, in others, they are sent as
binary information. How any command handles it is detailed below in the
command description.

The S and C represent the direction of the data (S->C represents something
the server sends to the client, C->S represents something the client sends
to the server.)

In terms of all binary values, we use MSB order (same as eutl used). MSB
order is also network byte order. This includes the initial length
information, as well as any ints or shorts that get sent inside the packets.
All packets are defined to have at least one word of text, followed by a
space, then followed by optional data (which can be binary.)

NOTE: Generally, the data the client sends to the server is text, but a fair
amount of data the server sends to the client is binary. This has somewhat
to do with who wrote what code, and also has to do that the S->C bandwidth
is going to more the more serious limitation - the client generally won't be
sending so much data that the its flow is much problem.

Note that all the commands as detailed below are up to date descriptions I
removed a lot of the old notes on this file, because they were out of date,
and while might be good ideas, were not all that relevant to how things
currently work.

Summary: Packets sent back and forth have a 2 byte header (MSB order) which
contains the length of the rest of the packet.

Implementation Notes
~~~~~~~~~~~~~~~~~~~~
We are using a TCP/IP socket. Other methods could be used, but the
present protocol does not make very good provisions for missing data, so
it needs to be something that corrects errors/does resends automatically
(or just doesn't get errors in the first place.)

For now, we set non blocking output on the server side. This means we don't
have to worry about internal buffering.

If the connection is lost (which will also happen if the output buffer
overflowing), the player is saved and the server cleans up. This does
open up some abuses, but there is no perfect solution here.

The server only reads data from the socket if the player has an action.
This isn't really good, since many of the commands below might not be actual
commands for the player. The alternative is to look at the data, and if it
is a player command and there isn't time, store it away to be processed later.
But this increases complexity, in that the server must start buffering the
commands. Fortunately, for now, there are few such client commands.

If it becomes a case where the client is requesting images/sounds, dual
channels could probably be used, since requesting that data is not related
to the actual playing of the game (or a special daemon that serves those
requests could also be done.) Better solution might be for that data to
be on a separate server that can be downloaded by more efficient mechanisms
(eg, ftp)

SUMMARY: TCP/IP sockets are used for exchange data. Server uses non
blocking i/o when writing to the socket, and the server only reads from the
socket when the player actually has time for an action.

Data Type Conventions
~~~~~~~~~~~~~~~~~~~~~
In the listing of the protocol commands below, different terms are used
to describe the data. This section is used to clarify what the different
types are:

string: A set of ASCII characters. If a protocol command has several string
        fields, then spaces are used to separate the strings.

length prefixed string: An 8 bit length field prepends the string. EG:
       <length><string>
       length prefixed strings are often used in cases where the string
       contains space, and the protocol command includes several strings
       or there are other fields following the string. The receiving
       end can decode the length, know how much data to copy and where
       the start of the next field is.

string value of integer data: This notes that the data is stored on
       the server (and client) as integer data, but it is converted to
       string data before sending (eg, sprintf(buf,"%d", val)).
       It means that the receiver will need to use atoi or the like
       to convert it back into the appropriate type.

binary X bit value (also X bit binary value): This notes that the data
       is sent as raw binary data of the given size. shorts would be
       16 bit, ints 32 bit, long longs 64 bit, etc.


Commands
--------
Object tags:  Many of the commands below refer to 'object tags'. Whenever
the server creates an object, it creates a unique tag for that object
(starting at 1 when the server is first run, and ever increasing.)  Tags are
unique, but are not consistent between runs. Thus, the client can not store
tags when it exits and hope to re-use them when it joins the server at a
later time - tags are only valid for the current connection.

The protocol commands are broken into various sections which based somewhat
on what the commands are for (ie, item related commands, map commands, image
commands, etc.)  In this way, all the commands related to similar
functionality is in the same place.

General Commands
~~~~~~~~~~~~~~~~
failure
^^^^^^^
    S->C: failure <protocol command> <failure string>

All fields are strings.

<protocol command> is the command (just the command portion, eg, version,
accountlogin, not with any additional data) that generated the failure.

<failure string> is a message which notes the failure - it will be displayed
to the player, so should be informative to the player so they can take
corrective action (omit illegal characters from their username, etc)

This command is used to denote failure in some way (as detailed in failure
string) of a protocol command. This does not mean that there was an error
in the protocol (which typically results in a command being dropped), but
rather that the server was unable to complete the given protocol request.

As of this writing (Jan 2010), this is used only in the account login code -
if the user enters incorrect login information, it will generate a failure
message.

The use of this protocol command, and it including the protocol command
which failed, better informs the client it needs to retry. For example, if
the user enters wrong account information, the server will send `failure
accountlogin wrong user name or password`. With this, the client can
display the message in the correct location, but also knows it needs to go
back to the point of asking for login information. draw_info provides no
mechanism to tell the client to retry an event.

This command is really meant for areas where the client is interacting with
the users. This command is not especially good in cases where the client
has sent several protocol commands of the same type - this command will only
tell that a command of that name failed, but may not include enough
information to note which of several commands failed.

Note that the format of message, while text data, can contain other
information. In particular, some messages may have the first 'word' be a
number which denotes some type of status - this will be detailed in the
protocol area for that command. For example:

failure accountaddplayer 0 That name is too long failure accountaddplayer 1
That character is associated with another account

The client should intercept that number and not display it, but this may
indicate that the command is retriable by changing a parameter - in the case
of accountaddplayer, if force is set, the second message there is not an
error.

version
^^^^^^^
    C->S: version <csval> [scval [vinfo]]
    S->C: version <csval> [scval [vinfo]]

All fields are strings.

Through the version command, the client and server exchange what version of
the protocol they understand. Neither send this in response to the other -
they should both send this shortly after a connection is established.

csval is the version level of C->S communications. scval is the version
level of S->C communications. vinfo is a string that is purely for
informative that general client/server info (ie, javaclient, x11client,
winclient, sinix server, etc). It is purely of interest of server admins
who can see what type of clients people are using.

If a new command is added to the protocol in the C->S direction, then the
version number in csval will get increased. Likewise, the same is true for
the scval.

As far as the client is concerned, its scval must be at least equal to the
server, and its csval should not be newer than the server.

The server does not care about the version command it receives right now -
all it currently does is log mismatches. In theory, the server should keep
track of what the client has, and adjust the commands it sends respectively
in the S->C direction. The server is resilant enough that it won't crash
with a version mismatch (however, client may end up sending commands that
the server just ignores). It is really up to the client to enforce
versioning and quit if the versions don't match.

scval and vinfo was added starting in 1020. Before that version, there was
only one version sent in the version command.

The version are currently integers, in the form ABCD. A = 1, and will
likely for quite a while. This will only really change if needed from
rollover of B.

B represents major protocol changes - if B mismatches, the clients will be
totally unusable. Such an example would be change of map or item sending
commands (either new commands or new format.)

C represents more minor but still significant changes - clients might still
work together, but some features that used to work may now fail due to the
mismatch. An example may be a change in the meaning of some field in some
command - providing the field is the same size, it still should be decoded
properly, but the meaning won't be processed properly.

D represents very minor changes or new commands. Things should work no
worse if D does not match, however if they do match, some new features might
be included. An example of the would be the C->S mark command to mark
items. Server not understanding this just means that the server can not
process it, and will ignore it.

NOTE:  Since all packets have the length as the first 2 bytes, all that
either the client or server needs to be able to do is look at the first
string and see if it understands it. If not, it knows how many bytes it can
skip. As such, exact version matches should not be necessary for proper
operation - however, both the client and server needs to be coded to handle
such cases.

NOTE: For the most part, this has been obsoleted by the setup command
which always return status and whether it understood the command or not.
However there are still some cases where using this versioning is useful -
an example it the addition of the requestinfo/replyinfo commands - the
client wants to wait for acknowledge of all the replyinfo commands it has
issued before sending the addme command. However, if the server doesn't
understand these options, the client will never get a response. With the
versioning, the client can look at the version and know if it should wait
for a response or if the server will never send back.

accountlogin and accountnew
^^^^^^^^^^^^^^^^^^^^^^^^^^^
    C->S: accountlogin <account name><account password>
    C->S: accountnew <account name><account password>
    S->C: failure <protocol command> <message>

<account name> is a length prefixed string of the account name. <account
password> is a length prefixed string of the password.

Under new login support (loginmethod >=1) the client will query the user for
account information - this sends that information to the server. In the
first place, the user is trying to log in with an established account, in
the second, the user is trying to create a new account.

It is up to the client to determine what is trying to be done - in general,
this means that player should be hitting a 'new account' type button or a
the like. It is up to the client to do double confirmation of passwords,
etc.

account name and account password are strings, with the first byte being the
length of the string.

If the login or creation fails, a failure protocol message is generated.
That is documented up above. The client should retry in that case.

accountplayers
^^^^^^^^^^^^^^
    S->C: accountplayers <num characters><char data1><char data2>...

[options="autowidth,header"]
|===========================
|Field|
    Description

|<num characters>|
    8 bit binary value noting how many characters on this account. It may be
    zero.

|<char data>|
    length prefixed data on character. The ACL_...  values in newclient.h
    define these. The format of each data value is:

    <len><type><value>

    <len> is an 8 bit value which is the length of type + value - in this way,
    the client can skip over the entire field in cases where it does not know
    the type.  If len is 0, it notes that there is no more information for
    this character.

    <type> is an 8 bit value which is an ACL_ type value.

|<value>|
    type specific - if a string value, it is just a string value. If binary,
    its length can be determined. Except for noted values, all value types are
    strings. Exceptions:

    ACL_LEVEL:: is a 16 bit binary value.
    ACL_FACE_NUM:: is a 16 bit binary value.
|===========================

NOTE: There is no requirement that the server sends all fields (may choose
to not send empty fields.) Likewise, there is no requirement they get sent
in a specific order.

This is a list of the players (characters) associated with this account. In
the case of new accounts, the num characters will be zero.

This is sent after the server receives a successful login or accountnew
request. The client can thus use the receipt of this command, even if
empty, to note that the user has logged in.

accountplay
^^^^^^^^^^^
    C->S: accountplay <char name>

<char name> string value of the character to play.

Play character of the given name. This must be one of the character names
returned by the accountplayers command - otherwise it will generate an
failure protocol command. On choosing a character, the game will log in and
play will start.

Upon receipt of this command, the server will do necessary setup to start
play. This removes the need for the addme command below.

accountaddplayer
^^^^^^^^^^^^^^^^
    C->S: accountaddplayer <force> <char name> <char password>

<force> - 8 bit binary data to force this association (see description
      below. This is not an optional field - it must always be sent.

<char name> length prefixed string of the character name.

<char password> length prefixed string of the characters password.

Add a character to the logged in account. Both the name and password are
needed. In the event that the given character is already associated with an
account (and not this one), a failure message will be generated unless force
is on.

The flow in that case would be user enter name/password and hitting submit,
client sends to server, server sends failure event to client saying
character is already associated with account, client asks player if he wants
to override that setting, and if they hit yes, command is then sent with
force set to 1.

On success, the server will send a new accountplayers command, with all
characters for this account. On failure, a failure message will be
generated.

The failure message for accountaddplayer does include the optional integer
parameter - if 0, the command is not retriable - if set to 1, then this
account may succeed if force is set.

createplayer
^^^^^^^^^^^^
    C->S: createplayer <name><password>

The player wants to make a new player - this is done on the client -
this basically tells the server to send the client information regarding
making new characters (races, classes, etc).

Loginmethod 1 supports following:
<name>: Length prefixed string - desired character name.
<password>: Length prefixed string - password

Loginmethod 2 adds the following (each of these blocks are length
prefixed so the server can easily skip lines). To make processing
simpler, the null byte is included in the processing here.

   race <race arch name>
   class <class arch name>
   <statname> <statvalue> (eg, Str 18)
   starting_map <map arch>
   choice <choice name> <choice value>

The client should query the player for these values through some method.
The statvalues that are sent are the values _before_ race and class
adjustments.

The <map arch> for starting_map is the value of INFO_MAP_ARCH_NAME as
returned by the 'startingmap' requestinfo.

The choice values are included in the race/class information as retrieved by
requestinfo. If the server is providing choices, it must also accept them
in return.

createplayer can return failure in case of invalid name, name already in
use, invalid race or class, stat value at of range, sum of stats too high,
etc.etc.

NOTE: Expected that this command will expand with new character creation
method.

accountpw
^^^^^^^^^
    C->S: accountpw <current account password><new account password>
    S->C: failure accountpw <message>

<current account password> is a length prefixed string of the current
password.

<account password> is a length prefixed string of the new password.

Tells the server to change the password for the current account. A failure
message is generated if something is wrong. If all goes well the server will
send the character list for the account.

addme
^^^^^
    C->S: addme

Tells the server that it should add me (the client) to the game.
Generally, the client will always send this command, but I suppose there
can be actions the client wants to do before being added.

Deprecated - this has been superseded by the accountplay command.

    S->C: addme_failed
    S->C: addme_success

This are responses to the last addme command. I really think these should
be discontinued, as they are one of the few messages which is just a
confirmation of a previous message. The addme_failed should really be
replaced with a terminate type of of message (player quits game, server
could inform us nicely and exit out). addme_success is really of no use -
client just throws it away.

NOTE: With account based login method, server will send the addme_success in
certain circumstances - this is really to tell the client that play has
started and hide any login/character selection information. However the
note above still applies - addme_failed could get replaced by a 'failure
addme ...' type response, and there is probably some use for having a
'success' type protocol response to tell the client that something has
worked - right now, this is done by the client seeing the next message in a
protocol state (eg, accountplayers follows an accountlogin request)

goodbye
^^^^^^^
    S->C: goodbye (Added in SC protocol version 1022)

Informs the client that the server has finished transmitting data to the
client. This is a bit cleaner than the client detecting a read error. In
theory, a C->S of the same type could be done, but I don't think it would
make a big difference for the server (is going to do the same thing
regardless of a clean connection drop or a bad one).

Also see the `setfacemode` command below.

Info Window Input/Output
~~~~~~~~~~~~~~~~~~~~~~~~

    C->S: ncom <packet> <repeat> <command>

(ncom = new command)

<packet> is a 16 bit binary value the server will send back through comc to
inform the client of execution of this command. It is up to the client to
determine how it wants to number these, but incrementing by one is the
easiest way.

<repeat> is a 32 bit binary value and is the repeat value, or a count value
used for instance for dropping.

<command> string value of the actual command data (north, whatever).

Client sends a command to the server. Ordinary commands (ie, north, west,
apply, maps, etc), might be sent, commands with options may be sent (ie,
'invoke create food of booze', 'cast medium fireball'). There are a few
special commands that can also be sent.

'fire' command is a special case. The server will handle repeat firing.

'fire_stop' will be sent to inform the server to stop firing. A different
command name has been chosen to make things easier on the server
('fire_stop' should be a 0 time command, with the rest of the fire commands
actually taking some time.)  In some cases, 'fire_stop' may be sent almost
immediately after the first fire (in cases where the player only wants to
fire once).

    S->C: comc <packet> <time>

(comc = completed command)

<packet> 16 bit binary value of command just completed.

<time> 32 bit binary value

This is used in the window of the ncom command above. packet is the command
number we just executed, and time is a 32 bit value represent how many
milliseconds the player is currently taking to execute commands. This
information can be used by the client to do some throttling.

    C->S: reply <text>

<text> is string data.

ends <text> as a reply to the last query command sent.

    S->C: query <flags> [text]

<flags> is string value of integer data.

[text] is optional text in string format.

Asks the client program for input. This is only used in a few places -
mostly in creating a character and login, but in fact anyplace in the server
that changes the input state (pl->contr->state, ST_*), should send a query.

<flags> are detailed in the <newclient.h> file, which is common to both the
client and server. The flags of relevance to this command are the CS_QUERY
flags. <flags> are sent in plaintext form.

The client is free to ignore the flags. However, if the server just wants a
single character as a reply, that is all it uses, even if the client sends a
long string (Server will use the first character.)

[text] is the question/prompt that should be printed. Right now, it is
typically just a ':'. Client should display it no matter what it is,
however. Text is an optional field. Note - as of 0.94.2, text may be multi
line, delimited by newlines. Client should handle this appropriately.

    S->C: drawextinfo <color> <type> <subtype> message

<color> string integer data - color to draw text in.

<type>  string integer data - type of message

<subtype> string integer data - subtype (flavor) of message.

<message> is a string representation of textual message. Content of message
may very well vary depending on the type.

Tell the client to draw specific text. Color are specified in newclient.h,
and is sent as a string (look for NDI values). The client is free to do
whatever it wants with the color information (it may very well ignore it.)

The list of types and subtypes is fully listed in the newclient.h file -
look for the MSG_TYPE fields. The subtypes of a given type are listed with
longer macro definition.

It is up to the client on how it wants to display the different message
types - it may have a nice graphic to display certain messages, route them
to certain windows, change color, etc.

Item Manipulation
~~~~~~~~~~~~~~~~~
move
^^^^
    C->S: move <to> <tag> <nrof>

<to> string integer data. Tag of destination object.

<tag> string integer data. Tag of object to move.

<nrof> string integer data. Number of objects to move.

This command is used to pickup/drop objects. If <to> or <tag> is zero, the
object is being moved from/to the ground. This command is used to move items
from a container into inventory and vice versa. if nrof is zero, all objects
will be moved.

examine
^^^^^^^
    C->S: examine <val>

<val> string integer data. Tag of object to examine.

Tells the server that I want to examine object <val>, where <val> is a text
string that represents that objects tag.

apply
^^^^^
    C->S: apply <val>

<val> string integer data. Tag of object to apply.

Tells the server that I want to apply the object <val>.

lock
^^^^
    C->S: lock <val><tag>

<val> binary 1 byte data. 0=unlock, 1=lock

<tag> binary 4 byte data. tag of object to lock

Tells to server to set the inventory lock flag of item tag to val.  val of 1
means that the item should be locked, 0 means unlocked.  The server should
send an 'upditem' command with new flags to reflect this change.

mark
^^^^
    C->S: mark <tag>

<tag> binary 4 byte data - tag of item to mark.

'marks' and item for secondary usage. Some actions in crossfire require an
action that uses another item (improvement scrolls, flint & steel). In order
not to rely on inventory ordering or other gimmicks, this 'marked' item is
used. Only one item can be marked at a time - server will only keep track of
the latest mark sent.  <tag> is a 4 byte binary value. The server will
generally send a drawinfo command informing the player, but there is no
especially easy way for the client to know what the marked item is (although,
client knowing this is not strictly needed)

inscribe
^^^^^^^^
    C->S: inscribe <version><spell tag><scroll tag>

<version> binary 1 byte value - version of inscribe command. Current, only
supported value here is 0.

<spell tag> binary 4 byte data - tag of spell to write. <scroll tag> binary 4
byte data. Scroll to write spell onto..

Player wants to write spell on scroll . This is roughly equivalent of manually
marking an item, readying the spell, and using the inscription skill.

item2
^^^^^
    S->C: item2 <location><tag1><flags1><weight1><face1><name1><anim1>
	<animspeed1><nrof1><type1><object2....>

<location> 4 byte binary data. Location of the object - 0=ground, any other
value is where it is - container or player.

<tag1> 4 byte binary data. Unique item tag for this object.  Note that the
server will use this command to note that objects have moved locations, so the
client should examine all objects it knows about for this tag - it should not
assume this is a new item.


<flags1> 4 byte binary data. Various flags on the item (curse, applied, etc).
They are detailed in newclient.h

<weight1> 4 byte binary data. The weight of single one of these objects (in
grams). The client will need to figure the total weight on its own. Note that
for containers, weight will the the total weight (that of the container plus
contents)

<face1> 4 byte binary data. This is the face number. These are not guaranteed
to be the same across different runs of the game (however, in reality, they
will only change on the one server if they make changes to the archetypes and
rebuild.) Some face information will be sent from the server to the client
before actually sending a face number.

<name1> length prefixed string. The name of the object.  Starting at SC 1024,
this name is two strings, with a null separation. The first of these strings
is the singular form, the second is the name to use for multiple (plural
version) The first byte (length) is the length for both of these strings. This
name information is just the information of what the object is called. It does
not include how many of the items there are.

<anim1> 2 byte binary data. This is the animation sequence id to use. The
server will send an 'anim' command for this before sending an item1 command
with this anim command.

<animspeed1> 1 byte binary data. How often the object should be animated. This
is the number of ticks that should pass between each animation (a value of 1
means it should be animated every tick.)  1 byte limits this to once every 255
ticks - I can't see anything being animated slower than that.

<nrof1> 4 byte binary data. How many objects comprise this item.  This is used
for the name field and calculating total weight.

<type1> 2 byte binary data. A numeric type id for the item. The only meaning
of this value is really for sorting - all armors will have type values the
same or near that each other. The client is free to ignore this.

Note that multiple items can be sent with a single item2 command - there is
only 1 location for all items, so all items have to be in the same spot, but
in the case of a players inventory, a single item2 with a large number of
items can be sent.

upditem
^^^^^^^
    S->C: upditem <flags><tag><vals>+

<flags> 1 byte binary value. flags determines what values are sent and to be
updated (for a definition of the flag values, see the UPD_ flags in
newclient.h file.)

<tag> 4 byte binary data. Tag of the item to update.

<vals> binary data of varying length. The data to be updated.  The format of
the data is the same as the item2 command above. The order of the data is that
the the UPD_ flags from LSB to MSB (thus, location, flags, weight, ...)

Only one item can be updated with the upditem command. An item command should
have been sent by the server before an upditem command is set.

delitem
^^^^^^^
    S->C: delitem <tag1>[tag2]...

<tag> 4 byte binary data. These are the tags of the items to delete. Multiple
tags can be sent with one delitem to delete multiple items, but as of this
writing (Jan 2010), the server only ever sends a single tag

Tells the client to delete items with the tag values. These items are
considered gone from the game, so the client should delete all reference it
has to them.

delinv
^^^^^^
    S->C delinv <tag>

<tag> string integer data.

Tells the client to delete items carried in/by the object <tag>.  Tag of 0
means to delete all items on the space tech character is standing on. This
command only affects the inventory of the object. To fully delete a container
object, a delinv followed by a delitem should be issued.

addspell
^^^^^^^^
    S->C addspell <tag1> <level1> <casting time1> <mana1> <grace1> <damage1>
    <skill> <path1> <name1> <display name1> <message1> <usage information>
	<requirements> <spell2 ....>

Tells the client to add the spell(s) listed to the list of spells
the client knows about. This will be sent at login, and again whenever
new spells are sent.

[options="autowidth,header"]
|===========================
|Field|
    Description

|<tag> - (4 bytes - int)|
    The ID number for the spell item. This is going to be unique, for each
    spell and will be used to refer to it henceforth. The string form of this
    should also be appended to the cast/invoke commands in order to cast the
    spell.

|<level> (2 bytes, signed int)|
    The level of the spell.

|<casting time> (2 bytes, signed int)|
    The time it will take to cast the spell, in server ticks.

|<mana>  (2 bytes, signed int)|
    The mana cost to cast the spell (may be zero)

|<grace> (2 bytes, signed int)|
    The grace cost to cast the spell (may be zero)

|<damage> (2 bytes, signed int)|
    The current damage done by the spell. Note that the meaning of this number
    is to a large part spell dependent, what damage it actually does will
    depend on how the spell works.

|<skill> (1 byte, unsigned int)|
    The skill that the spell uses to be cast, if zero, no skill is used in the
    casting of this spell.  The numbers are the same as for requestinfo
    skill_info

|<path>  (4 bytes, unsigned integer)|
    The path that the spell belongs to.  The client should determine the
    effect of this by comparing these values to both the spell_paths
    requestinfo data and the stats info concerning attunement/repulsion, etc.

|<face>  (4 bytes, signed int)|
    The number of the face that corresponds to the spell, the client can
    request this facenumber if they want to show a graphical spell
    representation.

|<name> (1 (non-zero)|
    length byte, followed by that many bytes of ASCII text) This is a name to
    identify the spell, which the client can use for display purposes, it
    should /NOT/ be used with the 'cast' command, whilst it might work, no
    such guarantee is made by the server. - Use tag instead.

|<message>|
    (2 length bytes (which may be zero) followed by that many bytes of ASCII
    text) The description of the spell. Note that this has an extra length
    byte because the messages may well be longer than 256 bytes in length.

	<usage information> (1 byte)
	       Only sent if 'spellmon 2' was setup by the client.
	       Values are:
                - 0: spell needs no argument.
                - 1: spell needs the name of another spell.
                - 2: spell can use a freeform string argument.
                - 3: spell requires a freeform string argument.

       <requirements> (1 byte of length, then that many bytes of ASCII text)
               Only sent if 'spellmon 2' was setup by the client.
               If the spell required items to be cast, then this is the list of
               those items. Comma-separated, potential number of items, singular
               names (like the ingredients for alchemy).
|===========================

updspell
^^^^^^^^
    S->C updspell <flags><tag><vals>+

<flags> 1 byte binary. Values include in this update. Uses the UPD_SP_.. from
'newclient.h'

<tag> 4 byte binary. Tag of the spell.

This updates some spell (of tag) with new values. The flags are 1 byte and
determine which values have been updated, and should be re-read.  Not all
fields may be updated by this command, only those that can be changed.

If new fields are added in future, they will extend the flags bitmask and the
order will remain the LSB order of the flags - that is, the value associated
with bit 1 set is sent first, then bit 2, etc.

The format of the values is same as the `addspell` command above.

Only one spell can be updated with the `updspell` command. A spell command
should have been sent by the server before an `updspell` command is set.

delspell
^^^^^^^^
    S->C delspell <tag>

<tag> 4 byte binary data.

Tells the client to remove its information about the spell. Tag is a 4 byte
value, the same as the one sent when the spell was added.

addquest
^^^^^^^^
    S->C addquest <code1> <title> <face> <replay> <parent> <end> <step> <code2
    ...>

Tells the client to add the quest(s) listed to the list of quests the player
is doing. This will be sent at login, and again whenever new quests are
started, if notifications is 1 or greater.

<code> - (4 bytes - unsigned int) The ID number for the quest item. This is
going to be unique, for each quest and will be used to refer
to it henceforth.

<title> (2 bytes length, unsigned int, then string of specified length)
The quest title.

<face>  (4 bytes, signed int)
The number of the face that corresponds to the quest, which will be sent
before this packet if needed.

<replay> (1 byte, unsigned int)
If 1, then the quest can be replayed, else it can't.

<parent> (4 bytes, unsigned int)
Code of this quest's parent, 0 if top-level quest.

<end> (1 byte, unsigned int)
If 1, the quest was completed.

<step> (2 bytes length, unsigned int, then string of specified length)
The current step's description, can be an empty string (length 0).

updquest
^^^^^^^^
    S->C updquest <code><end><step>

<code> - (4 bytes - unsigned int) The ID number for the quest item.

<end> (1 byte, unsigned int) If 1, the quest was completed.

<step> (2 bytes length, unsigned int, then string of specified length) The
current step's description, can be an empty string (length 0).

This updates some quest (of tag) with new values, if notifications is 1 or
greater.

Only one quest can be updated with the `updspell` command. A `addquest`
command should have been sent by the server before an `addspell` command is
set with the same ID.

addknowledge
^^^^^^^^^^^^
    S->C addknowledge <code1> <type> <title> <face> <code2 ...>

Tells the client to add the knowledge item(s) listed to the list of things
the player knows. This will be sent at login, and again whenever
new knowledge is learnt, if 'notifications' is 2 or greater.

<code> - (4 bytes - unsigned int) The ID number for the knowledge item. This
is going to be unique, for each knowledge and will be used to refer to it
henceforth. It is the same number the player sees with the 'knowledge'
commands.

<type> (2 bytes length, unsigned int, then string of specified length) The
knowledge's type, as defined in the knowledge_info reply.

<title> (2 bytes length, unsigned int, then string of specified length) The
knowledge title.

<face>  (4 bytes, signed int) The number of the face that corresponds to the
knowledge item, which will be sent before this packet if needed.

Player Object and Stats
~~~~~~~~~~~~~~~~~~~~~~~
player
^^^^^^
    S->C: player <tag><weight><face><name>

All fields are the same as described in item above. The only difference is
that player tells the client that this is the central object it needs to care
about.

stats
^^^^^
    S->C: stats <stat1><val1><stat2><val2>...

<stat> 1 byte binary data. One of the CS_STAT values from 'newclient.h'

<val> binary data. All are 16 bit values except for following exceptions:

weight limit:: 32 bit

speed, weapon_sp:: 32 bit value. This is float converted to an
	   integer by multiply by FLOAT_MULTI. The client needs to divide by
	   that value to get it back to a float.

range, title::  Length prefixed strings.

experience:: if CS_STAT_EXP64 is sent, 64 bit experience
		value. 64 bit is the only option now - 32 bit exp is no longer
		sent.

skill experience:: 64 bit.

spellpaths:: 32 bit. Only sent if spellmon is set in setup.
        The CS_STATS_RACE_xxx and CS_STATS_BASE_xxx are only sent if
        extended_stats was used in setup.

This is a server message that tells the client values of the various stats.
Multiple stats can be sent on one command.

Image Information
~~~~~~~~~~~~~~~~~
anim
^^^^
    S->C: anim <num><flags><face1><face2>...

<num> 2 byte binary data. animation number we are defining.  The server will
only send the anim command for a particular <num> once per run - the client
needs to keep track what has been sent. On new runs, anim commands will be
resent.


<flags> 2 byte binary data. Currently unused, but is included because I think
there may end up being cases were more about the animation than just the num
and faces are needed.

<face1>... 2 byte binary data. This is the various faces that comprise the
animation sequence. The number of faces can be determined by checking the
length of the packet. These values correspond in the same way as all
references to face do.

This command informs the client of an animation sequence. The client is
responsible for animating the objects in the inventory window, and upditem and
other items command will refer to the animation number with num above. All
values are 2 byte binary values.

Note that how fast the object is animated is contained in the item commands.

image2
^^^^^^
    S->C: image2 <face><set><len><data>

<face> 4 byte binary data - face number.
<set> 1 byte binary data. Which faceset the image belongs to.
<len> 4 byte binary data. Length of face data.
<data> Binary data - actual face (png) information.

Sends a png version of an image to the client.

face2
^^^^^
    S->C: face2 <num><setnum><checksum><name>

<num> 2 byte binary data. Face number.
<setnum> 1 byte binary data. Which set this face belongs to.
<checksum> 4 byte binary data. Checksum of face data.
<name> character data

Informs the client that image <num> of faceset <setnum> is associated with
<name>. This is used when the client is caching images. In normal operation,
when the server runs across a face that it hasn't sent the client, it sends a
png for that face. If the face mode is none, the server then sends this
command. The client can then check to see if it might have cached this face,
and if not, should then request it from the server. Note that the num to name
mappings can change between server and different runs of the server. For this
reason, this data needs to be sent each time it is run. The client should be
able to load/determine what face to load via the name.

askface
^^^^^^^
    C->S: askface <num>

<num> string of integer value.

Requests that the server send the client face <num>. The server will
use values from setup to determine what faceset to send.

smooth
^^^^^^
    S->C: smooth <face><smoothpic>

<face> 2 byte binary data - face number
<smoothpic> 2 byte binary data. Face to use for smoothing.

This command informs the client on how to smooth an image.  Following are the
facenbr of the picture involved in the smoothing algorithm. See doc on
smoothing on how to use them.  The server will send this to the client just
like it sends faces, but client can also make explicit requests.

asksmooth
^^^^^^^^^
    C->S: asksmooth <face>

<face> string of integer value.

Ask server to send a smooth sequence. Server will respond with a
smooth command. <facenbr> is an integer telling server which face
we want smooth information on.

Map Update
~~~~~~~~~~
map2
^^^^
    S->C: map2 <coord1><len1/type1><data1><len2/type2><data2>...<coord2>

This is an update of the map2 command above. It is meant to be
extensible. It is also meant to incorporate the ideas of the
extended map info command.

All data is in standard binary form.

<coord> 2 byte binary

    	the coord values are length + x + y values.
       	The data represented looks like this:

       	first 6 bits: The x coordinate (0-63)
       	next 6 bits: the y coordinate (0-63)
       	LSB 0-3:  Has the following meaning:
       	    0: Normal coordinate
       	    1: Use this coordinate for scroll information and not an
       	       actual coordinate. This removes the need for the
       	       mapscroll command. Note that coordinate are still
       	       modified with the MAP2_COORD_OFFSET as described below
       	       - as an example, if 14, 14 is passed, that means
       	       effective scroll of -1, -1. This should only be set in
       	       the first coordinate value. Another (real) coordinate
       	       pair will immediately follow this coordinate pair.
       	    2-15: Unused/reserved.


       	The x & y coordinates are offset by MAP2_COORD_OFFSET (15).
      	This is necessary because there may be effects noticeable to the
       	player (light sources) that to the left/above the visible map. By
       	using this offset, we can use a coordinate like 10, 27 to denote
       	that something is 5 spaces above the top of the map.

<len/type> 1 byte binary data.  This describes the data that is to follow. If
this byte is 255, then this is a coordinate termination byte - this means a 7+
length field of type 1f is not possible.

The top 3 bits (len) denote the number of bytes that follow - it is possible
that this is zero, to denote all the relevant information is included in the
type. If this is 7 (all bits set) then the following byte is an additive
length value.  Currently, nothing has a 7+ bit length.

The bottom 5 bits is the type of data - this allows for 31 different types of
data (0-31/0x0-0x1f). The meaning of the data itself depends on what the type
is. List of various types:

       	0x0:: Denotes this space should be cleared. Length in this
       	    case should also be zero, as there is no data that
       	    follows. Clear in this context means that all data
       	    associated with the space should be purged, eg, images,
       	    sound, darkness, whatever.

       	0x1:: Darkness information - a single byte follows on how
       	    light/dark the space is. 0 is completely dark, 255 is
       	    full bright. Note that 0 will never be sent - if the
       	    space is completely dark, players won't be able to see it.

       	0x2:: Not used. Possible future enhancement to hold sound data.

       	0x3:: Not used. Possible future enhancement to hold light sources.

       	0x4 - 0xf:: Unused

       	0x10 - 0x19:: Image information. Layer 0x10 is the lowest, 0x19 is the
       	    highest. There are several forms of this data depending on the
       	    length:

       	    2 bytes: This is only the face number.
       	    3 bytes: <face num>[<smooth>|<animspeed>]
       	    4 bytes: <face num><animspeed><smooth>

       		smooth is a single byte for smoothing information. if
       		face_num has the high bit set, then this object has an
       		animation, and the byte after the animation is animation
       		speed (see below for more details). Smooth information
       		may still be sent for animations, and that would follow
       		the animspeed.

       	    If face is 0, that means that the face (or animation)
       	    is no longer visible, and smooth information should also be
       	    cleared.

       	    For animations:
           		face will have the high bit set to denote it is not a
           		face but an animation id.

           		MSB-1, MSB-2: These are used to denote type of animation:
		        0: Normal animation - start at first phase, etc.
                1: Randomize - randomize the animation phase & timing.
		        2: Synchronize - this animation should be in the same phase
		          as other animations with the same id. Used for things
		          like oceans.

          		Like the itemcmd, the server will send information for
		        the animation to the client before using the animation
		        id.

		Animations have an extra byte after the animation id -
		this is the animation speed. Like the itemcmd, it is
		how long, in ticks, between animations. 1 means it should
		be animated every tick.

Some notes:

Coordinates outside the viewable map may be sent. In these cases, it means
that a big image that extends onto the viewable map is on that space. For big
images, only the bottom right coordinate is sent - this is why it may be off
the viewable coordinates. For such spaces, only the actual big image itself
will be sent for that space.

Note that all operations are considered updates to the space (eg, new image,
new light level, etc). The exception would be the clear command, which means
clear all data with the space.

Note that while not used now, order of these subpackets is important.  A clear
(0x00) followed by other data should be parsed in that order - clear the data,
then process the data. In contrast, sending data followed by a clear byte
makes no sense. This functionality will likely be used in the future - for
example, if 6 layers need to be cleared and the other 2 remain the same, it
will be more efficient to send that clear byte followed by the 2 layers to
redisplay instead of sending 6 layers with an empty face..

Relative to the map1/map1a commands, this is more bandwidth intensive -
basically, an additional byte is needed for each piece of data sent.  Thus, on
a 25x25 map, if we presume 1.5 objects/space, this is an extra 940 bytes to
send. OTOH, typically the entire map is not being sent - only those bits that
change, so this may not be as costly as that.

If the player is using smoothing, this may actually save bytes, as the
redundant coordinates and type/length information does not need to be sent.
With the map2 command, the mapextend command is deprecated and is not used.

General design notes:  For data types that vary in length because of optional
data, the required data should be sent first, followed by optional data if
appropriate. An example of this is the face information - we send the 2 face
bytes first, then follow that with optional data (smoothing and/or animation
data). This makes parsing on the client easier - basically, the client should
be able to parse the data a byte (or pairing at a time).

tick
^^^^
    S->C: tick <tickno>

<tickno> 4 byte binary data (unsigned)

This just tells the client what the current tick is. Right now, the client
only uses this to know when to animate the images that the client is
responsible for animating. This will only be sent if negotiated with the setup
command.

map_scroll
^^^^^^^^^^
    S->C: map_scroll <dx> <dy>

<dx><dy> string of integer value.

This tells the client to scroll the map dx and dy direction. dx and dy will
typically be -1, 0, or 1, depending on how the player moved.  <dx> and <dy>
are sent as plaintext. positive values are down and to the right respectively,
negative values are opposite.

mapredraw
^^^^^^^^^
    C->S: mapredraw
	Requests that the server resend the entire map to the client -
	can be useful if the client or client player knows that the map
	is out of date/corrupted. Note that the server is not required
    to honor this command, and currently just ignores it.

newmap
^^^^^^
    S->C: newmap

This tells the client to clear the map state. Used when player is moving
between maps to invalidate all map state information in the client.

magicmap
^^^^^^^^
    S->C: magicmap <width> <height> <px> <py> <data>

<width> <height> string of integer values - width & height of magicmap

<px> <py> string of integer values. Players position on magic map.

<data> binary data - one byte per space. Low nibble contains color
information, high nibble contains FACE_FLOOR and FACE_WALL (see newclient.h)
to denote nature of object on that space. This string of data represents the
space from left to right, then up to down.

Sound
~~~~~
sound2
^^^^^^
    S->C: sound2 <x><y><dir><volume><type><action><name>

'x' and 'y' contain one byte of binary data each, representing the location of
the sound relative to the player.

'dir' contains one byte of binary data, indicating which direction the sound
is moving, using the standard direction map (values 0 through 8).

<volume> 1 byte binary data. Value of 1-100, arbitrary intensity of sound.

<type>   1 byte binary value. The major sound type.

<action> Length prefixed string. String describes subtype information The
length is an 8-bit value.

<name>   Length prefixed string. Name of the source of the sound - typically
object name, but in the case of player generated sounds, will be the race of
the player. The length prefix is an 8-bit value.

Plays a sound. See the 'doc/Developers/sound' document for more information.

music
^^^^^
    S->C: music <song>

<song> string data of sound to play.

Change background music. Server will send NONE as the string to stop any
music from playing. This song data is set in a map property. (Due to
someone forgetting to update this file when he/she implemented the
command, it is unknown what exactly should be done with the string
parameter, is it a filename? If yes: relative what?)


Miscellaneous
~~~~~~~~~~~~~
beat
^^^^
    C->S: beat

No-op command, used in conjunction with the `beat` setup command.

lookat
^^^^^^
    C->S: lookat <dx> <dy>

Where 'dx' and 'dy' are textual representations of integers.

Client (player) is looking at space 'dx', 'dy'. 'dx' and 'dy' are delta
offsets from the player (client doesn't know where the player is on the map,
so this is the only real way to deal with it.)  This is only a request to the
server - a response will typically come back in drawinfo commands.

setup
^^^^^
    C->S:
    S->C: setup <option1> <value1> <option2> <value2>

All arguments are strings, and the server will make the necessary conversions.

Client first sends a setup command to the server to request a change in some
value (option1). This can be at any point during the life of connection
between client and server.

All data in the setup command is in ASCII text form. options and values can
not have whitespace - the client and server use whitespace to split the
options and values.

The server only sends a setup command in response to one from the client. The
sc_version should be updated in the server if commands have been obsoleted
such that old clients may not be able to play.

There are really 2 set of setup commands here:

. Those that control preferences of the client (how big is the map,
what faceset to use, etc).
. Those that describe capabilities of the client (client supports
this protocol command or that)

.Setup Options
[options="autowidth,header"]
|===========================
|Command|
        Description

|beat|
        Ask the server to enable heartbeat support. When heartbeat is enabled,
        the client must send the server a command every three seconds.

        If no commands need to be sent, use the `beat` no-op command. Clients
        that do not contact the server within the interval are assumed to have
        a temporary connection failure.

|bot (0/1 value)|
	    If set to 1, the client will not be considered a player when
	    updating information to the metaserver. This is to avoid having
	    a server with many bots appear more crowded than others.

|darkness (0/1 value)|
	    If set to 1 (default), the server will send darkness information
	    in the map protocol commands. If 0, the server will not
	    include darkness, thus saving a minor amount of bandwidth.
	    Since the client is free to ignore the darkness information,
	    this does not allow the client to cheat. In the case of the
	    old 'map' protocol command, turning darkness off will result
	    in the masking faces not getting sent to the client.

|extended_stats (0/1 value)|
	   If set to 1, the server will send the CS_STATS_RACE_xxx and
	   CS_STATS_BASE_xxx values too, so the client can display
	   various status related to statistics. Default is 0.

|facecache (0/1)|
	    Determines if the client is caching images (1) or wants the
	    images sent to it without caching them (0). Default is 0. This
	    replaces the setfacemode command.

|faceset (8 bit)|
	    Faceset the client wishes to use. If the faceset is not
	    valid, the server returns the faceset the client will be
	    using (default 0).

|loginmethod (8 bit)|
        Client sends this to server to note login support. This is basically
        used as a subset of the csversion/scversion to find out what level of
        login support the server and client support. Current defined values:
        0: no advanced support - only legacy login method
        1: account based login (described more below)
        2: new character creation support

        This list may grow - for example, advanced character creation could
        become a feature.

|map2cmd: (1)|
            This indicates client support for the map2 protocol command.
	    See the map2 protocol details above for the main differences.
        Obsolete: This is the only supported mode now, but many clients use
        it as a sanity check for protocol versions, so the server still
        replies. It doesn't do anything with the data

|mapsize x X y|
	    Sets the map size to x X y. Note the spaces here are only for
	    clarity - there should be no spaces when actually sent (it
	    should be 11x11 or 25x25). The default map size unless changed
            is 11x11. The minimum map size the server will allow is 9x9
	    (no technical reason this could be smaller, but I don't think
	    the game would be smaller). The maximum map size supported in the
	    current protocol is 63x63. However, each server can have its
 	    maximum map size sent to most any value.

	    If the client sends a mapsize command out of valid range, the
	    server will respond with a mapsize with the maximum size
            the server supports. Thus, if the client wants to know the maximum
            map size, it can just do a 'mapsize 0x0' and it will get the
            maximum size back.

	    The server will only set the mapsize for the client if both x & y values
	    are valid. For example, if the maximum map size is 25x25, and the
	    client sends a 31x23 mapsize request, the mapsize will remain at
	    11x11 (default) and the server will send back a mapsize 25x25
	    setup command.

	    When the values are valid, the server will send back a mapsize
	    XxY setup command. Note that this is from its parsed values,
	    so it may not match stringwise with what the client sent, but will
	    match 0 wise. For example, the client may send a 'mapsize 025X025'
	    command, in which case the server will respond with a
	    'mapsize 25x25' command - the data is functionally the same.

	    While the server in theory supports non square viewing regions,
            this has not be tested.

            The server will send an updated map view when this command is sent.

|notifications (int value)|
      Value indicating what notifications the client accepts.
      It is incremental, a value means "all notifications till this level".
      The following levels are supported:
       1: quest-related notifications ("addquest" and "updquest")
       2: knowledge-related notifications ("addknowledge")

|num_look_objects (int value)|
	    The maximum number of objects shown in the ground view. If more
	    objects are present, fake objects are created for selecting the
	    previous/next group of items. Defaults to 50 if not set. The server
	    may adjust the given value to a suitable one; this applies to both
	    the lower and the upper limit. Returned is the number of items
	    actually used; this value can differ from the given one if it has
	    been adjusted.
	    Updated ground view will be sent to the client if the connection
	    is for a player.

	    Note: the requested int value is the total number of objects
	    including fake objects (prev/next group and transport icons). The
	    intention for this option is to enable clients to use a fixed
	    number of slots for displaying ground view objects.

|sound2 (bitmask)|
            New sound support. Check above for more information.
	    1=send sound effects
	    2=send music
	    64=mute sound; same as "sound" ncom command

|spellmon (0/1/2)|
	    If set to 1 the client has indicated that it wishes to be
	    sent the spell list and updated when it changes.
	    If set to 2, like 1 but with extra information (see "addspell").

|tick (0/1)|
	    If set, the client want tick commands so it knows animation
	    timing.

|want_pickup (0/1)|
	    If set, the client wants to be informed of pickup mode changes.
	    Mode will be sent when the player successfully logs in, and
	    afterward any time the value is changed (for instance by the
	    player through the direct use of 'pickup' command).
	    The value is the same bit format the client sends through menus
	    and such.
|===========================

requestinfo and replyinfo
^^^^^^^^^^^^^^^^^^^^^^^^^
This section describes the requestinfo and replyinfo commands.
Because these commands may handle different types of data with different
return formats, this section is formatted a bit differently to make
it easier to read the different structures.

    C->S: requestinfo <info_type> [options]
    S->C: replyinfo <info_type> [options] <data>

<info_type> is a string value, describing what information is wanted/sent
[options] is string data - specific to the type of data.
<data> is the actual data. The format of this data will vary based on
what the info_type is.

The requestinfo command is a general purpose way for the client to request
some piece of data the server may have. The server still needs to be
coded to respond to the specific info_type, but if the passed info_type is
not supported, the server will still respond with the replyinfo, but with
an empty data list.

This mechanism allows the client to send requests for data and not need to
do complicated checking if the server would understand the specific
request - if the server understands it, the data gets sent back. If the
server doesn't understand it, the client gets no data, but does get the
replyinfo so that it knows that the server does not support that
particular aspect.

Only one info_type is allowed for each requestinfo. If the client
requests many pieces of information (say image sets available, spell
listings, etc), it should send multiple requestinfos.

[options] is specific to the info_type - it could be a range of values, or
empty.

Requestinfo requests will not change any data on the server - the setup
command should be used for that. The requestinfo just requests data.
Note that since the requests can be made before a player logs in, the
requestinfo command will not generally support getting information related
to the player object.

As a general rule, the information returned is static - if the
client makes a second requestinfo with same parameters during the
same session, it will get the same data back. Thus, the client
can safely cache the data instead of making multiple requests.
There could be rare cases where information changes (eg, server
admin is updating the new file), but these would be rare and
generally are not something that needs to be designed for.

.Supported Info Types
[options="autowidth,header"]
|===========================
|Type|
        Description

|image_info (no options)|
         Request basic image information the server has. The data is
         sent in text format - the replyinfo is newline terminated.
         Since the packet length is sent in the header, that is used
         to figure out the length of returned data.

         Line 1: The last image number the server has. Note that
         there is no image 0, so this also amounts to the number of
         images if you start counting from one.

         Line 2: checksum of all the image name information. This can
         basically be used to determine if the number to name mapping
         is the same, eg, if on server 1 the total is 123456, and the
         player goes to server 2 and the total is the same, we can say
         with a high degree of confidence that the name to number
         mappings are the name. If instead the numbers differ, we
         know we can't rely on using the same mappings.

         Line 3+:The image set information the client has. The format
         is the same as the format in the image_info file, sans
         comments. The server will ignore any parameters the client
         sends.

         An example response:

         replyinfo image_info
         3512
         1169234
         0:base:standard:0:32x32:none:The standard image set.
         1:clsc:classic:0:32x32:none:Classic and new styling.


|image_sums <start> <stop>|
    	Request the image number to name (and checksum) values - in
      	this way, the client can build all images before play starts
      	and also request any missing images. The returned data is

       	image_sums <start> <stop> <imagenum><checksum><faceset><namelength><name>

      	There is an initial space after the stop value, but no spaces
       	after that point. The <start> and <stop> values are ASCII
       	text (same format as it is sent to the server in). The start
       	and stop values are inclusive - thus, if the start is 0 and
       	the stop is 100, 101 checksums will be set.

        imagenum is 16 bit binary data.
        checksum is 32 bit binary data. It contains the checksum for
             the image in the current selected set, and will use whatever
             fallback logic the imagesets specify.
        faceset is 8 bit binary data. It contains the actually selected
             faceset.
        namelength is 8 bit binary data. It is the length of the
            name field below, including the null terminator.
        name is character data. It is null terminated to make processing
            easier - in this way, the client doesn't need to copy the data
            to make it null terminated.

        Note that due to possible OS system constraints on the maximum
        single write supported to a socket, the complete set can not
        be requested at once - instead, the images information should
        be requested in blocks of less than 1000. The server will not
        process a block larger than 1000 at a time. Smaller blocks
        may be desired if the client wants to try to reduce the
        potential lag caused.

        Multiple requests for all the information can be sent at once,
        as the server will buffer the response data, but constraints
        prevent the server from sending the entire data back in one
        replyinfo (one being that the data would be beyond 65535
        bytes, so the length information in the packet would not be
        accurate.)

        If the client sends invalid data (stop is less than start,
        missing stop parameter, stop is beyond the number of images,
        or asking for more than 1000 at a time), the reply will just
        be an empty list.

        Note that the server will track that it has sent the face
        information for the requested images, and thus will not send
        it again (unless requested via requestinfo). Thus, this
        request should always do the right thing with the returned
        information.

|exp_table|
        This requests the experience table (what exp is needed for
	    each level) from the server. With this data, the client can
	    easily display how much experience is needed for the different
	    skills or total exp value for next level. Data format:

	    <num_levels>: uint16 - max level/how many exp values follow.
        <level1> ... <level num_levels>: uint64 - amount of exp needed
            for the level.

       	Note that num_levels and the actual exp values are transmitted
        as binary values.

|knowledge_info|
      This returns the list of knowledge types the server uses.
      One item per line, in the format:
        type:display name:face number:attempt

      'type' and 'display name' are strings.
      'attempt' is 0 if the knowledge type isn't alchemy-like, 1 if it can be 'attempted'.

      The first line will always contain empty types and names, to indicate the
      face of the 'generic' type.

|skill_info (empty or '1')|

    	This returns the skill number to skill name mappings. In this
       	way, new skills can be added in the server, and the client can
       	use this new skill information with no changes to the code.

        All data below is in text format. If the additional value is empty then format is:

        stat number:skill name

        else format is

        stat number:skill name:face number

        Where stat number is the number that will be used to send
        that skill information. Example:
        141:lockpicking
        142:hiding
        143:smithery

|spell_paths|

        This returns a list of all spell paths in the game, along with
        the number associated with them. This should be used to parse
        spell_path data in the stats command. The number is a bitmask
        but is sent as a decimal value.

      	All data is sent in text format. Format is:

        number:name

        eg

        16:missiles

|race_list|
        Returns the races players can choose.
        The names can be used to request more information with race_info.
        Reply format is: replyinfo race_list |race1|race2|...|racen

        Note that the names returned are archetype names, and thus not
        really suitable to display to the player.

|race_info|
        Returns information about specified playable race (one from
        race_list above). Format is:

        name <namelen><namedata>
        msg <desc len><description>
        stats <statno1><adj1><statno2><adj2>....0
        choice <len><choice name><len><choice description>
             <len>arch name<len>arch_desc(repeat arch)0

        name is the name that the player sees (data returned by
        race_list above is archetype name). It is a length
        prefixed string.

        stats is a literal string value, and what follows are binary
        statno and adjustment values. statno uses the CS_STAT value
        that is used by the stats command, and the type of adjustment
        matches that for stats (eg, if statno1 is a 32 bit type, a 32
        bit type will be used here). Any/all of the CS_STAT types
        could be sent, but in general only a subset will be sent. The
        server will only send stats which are not zero, so the client
        should assume all stats that are not sent have a zero value. 0
        is used for a statno to denote there are no more stats.

        description is a text description. It is length prefixed (2
        bytes) to allow for possible expansion (with it having a known
        length, additional fields could be set to follow the
        description. NOTE: The length parameter here is unusual in
        that most strings use only an 8 bit length value, but for
        messages that would not be long enough, hence the 16 bit value.

        choice is a choice of values to present the player for character
        creation - it is a choice of one of many archetypes - it could
        be skill, ability, or potentially even choice of items. All
        of the field in the choice are 1 byte length prefixed, since
        they may contain spaces. An example values (where | would
        be the length value - | is used to improve readability):

        choice |race_choice_1|Choose a racial skill|
            skill_smithery|Smithery|skill_jeweler|jeweler0

        When the client replies in the create player, it would include
        the choice name and archetype name, eg:

        choice race_choice_1 skill_smithery

        This makes it easier for the server to check the returned values -
        if it is a racial skill, it knows to check the race, if a class
        skill, it checks the class, etc.

        There is currently no way to do something like 'choose 2 out of
        4 skills' - however, this could be done by using multiple choice
        (choice race_choice_1 ... choice race_choice_2 ...)

        For the choice command, all the passed values come in pairs -
        choice name/choice description, arch_name/arch_description

        Note that the race archetype name will be included in the replyinfo
        header, eg, 'replyinfo race_info dwarf_pl'.

        Note also that the order of the fields here is not fixed - the
        server could send them in 'stats, msg, name' order - the
        client should be able to handle any order. Note also that it
        is conceivable that the server will send multiple stats
        command if new stats are to be sent - in this way, the client
        can process as much as possible, and then stop processing once it gets
        something it does not understand.

|class_list|

|class_info <class name>|
        The format of the data returned is exactly the same as for the
        race_.. command of the same name - the only difference is this
        is class information.

|startingmap|
        Sends data about starting map choices to the client. Format is:

        <type><length><data>

        <type> is a single byte binary - the INFO_MAP values define this.
        <length> is a 2 byte binary - length of following data. This is
                two bytes because some of the string data that can be
                sent here will be beyond 255 that a single byte can handle.
        <data> is actual data - as of now, this is all text data (name,
                description, etc), but could potentially be binary data
                (face number)

        A single map info command will contain information on all the maps.
        Once the client gets an INFO_MAP_ARCH_NAME, all following map information
        that follows is for that map until the next INFO_MAP_ARCH_NAME is found
        or the end of the packet is reached.

|newcharinfo|
        This sends information to the client for creating a new character through
        the 'createplayer' command. The information sent multiple length prefixed
        strings - each string corresponds to an entire line/variable set.

        The idea behind this is that new types/options for character creation
        can get added without needing to rewrite the entire protocol commands
        or increase the protocol version - the client requests this information
        and see if it understands all the data the server wants. If so, it
        can then create a character.

        While this setup looks fairly complicated, the simplest way
        for the client to handle it is to just make sure it
        understands all the variables present (ignoring type) and it
        gets all the ones it expects, and if it doesn't, just throw up
        an error that client needs to be updated in order to create a
        character on that server. One reason for the extra complexity
        here (instead of just making a set of assumptions that are
        fixed in the protocol) is that lots of discussions have gone
        on about character creation changes, so this allows for many
        of them.

        <type> <variable name> <values>
            type is a single character which denotes the type of data
            that is in this line, currently values are:

            R: required - needed value in the createplayer command.
            O: optional - if not present in createplayer, server can fill in
                 some default value. If a client does not understand
                 an Optional type but understands all the other types,
                 it could still create the character.

            V: values - this contains some values which are used in character
                creation but may not be sent back in the actual
                createplayer command. An example here is the number of
                points the player has to spend on stats - the client
                does not send that back, but rather sends the actual
                stat values during the createplayer command, but it
                needs this value to do so.

            I: Informational - some piece of information that the
                client should communicate to the player. An example
                here could be a requestinfo that is related to class
                or race choices for new characters - one may not want
                to put it in the news since it is only relevant for
                people creating new characters.

        <variable name> name of variable - race, class, map, etc are
            all possible names. The only constraint on name is that
            it can not contain any spaces.

            Short description of variables currently supported:

            points: How many total points the character has to spend -
                at current time these are just used for stats, but
                possible in future they could get used for other
                things.

            race, class: Notes that race and class information need to
                be sent to the server. This is a fixed assumption
                now, but if at some point someone wanted to remove
                either races or classes (or both) and reduce the
                number of choices, this provides a mechanism to do so.

            statrange: The minimum and maximum value for a stat.

            statname: The name of the different statistics. Like race
                & class above, this is a fixed assumption now, but if
                a stat was to get removed, or a new one added, this
                provides a mechanism for the client to know it.

            startingmap: Provide choice of starting maps for the player.
                List of maps is provided through the 'startingmap'
                requestinfo command.

        <values> value tends to be specific to the variable itself.
            In general, the client will need to be able to parse each
            required and value variable - if it is unable to do so, it
            is likely it will not be able to properly generate a
            character. requestinfo is used for some variables to note
            that a requestinfo protocol command should be used to
            retrieve additional data. Note that the client will have
            to have support for that requestinfo command, and still
            has know the actual mapping of variable name to
            requestinfo name. In the case of race and class, it would
            have to do the race_list/class_list, and when it gets the
            response from that would then have to know to do the
            race_info/class_info

        Below is a sample for first set of supported values (note in
        the actual protocol, each of these lines is prefixed by a
        single length byte). Note that all values should be
        considered case insensitive. Each line is also null
        terminated by the server.

        V points 200
        V statrange 1 20
        V statname Str Dex Con Wis Cha Int Pow
        R race requestinfo
        R class requestinfo

        Possible future extensions (these are provided as an example):
        V statpointcosts 0 1 2 3 4 ....
          : If different stat points have different costs (nonlinear) this can
          be used to return a list of the costs. Instead of values, this could
          also point to a requestinfo.
        O skill skill1 skill2 ...
          If at some point the player can choose some of the skills for their
          character, this would be used.

|news/rules/motd|
        Send the news/rules/motd file information to the client. This
        is mainly useful as a way for the client to easily capture
        this information instead of getting it from drawinfo commands.
        This is most useful in that the client can more easily choose
        where to display this information. The sent data is null terminated
        to make string handling easier on the client.
|===========================

Sample Session
--------------
The client first opens a connection to the server.

    S->C: version 1001
    C->S: version 1001

The client/server are exchanging version information, to verify that
they can both properly communicate with each other. If there is
a mismatch, one or both of the sides might close the connection.


    C->S: setfacemode 2

The client is informing the server that is wants to use XPM images. Note
that setfacemode is an optional command - if the client wants to live with
the default (XPM) mode, it doesn't need to send this.

    C->S: addme
    S->C: addme_success

Client is informing the server it wants to be added to the game. Server
is telling client that the command has succeeded, and it will then
be added.

NOTE: I am not sure if this is the exact order of the next few commands,
since a whole bunch of stuff is being done at once.

    S->C: pixmap (All that the map command uses will be sent.)
    S->C: map (display starting town map.)
    S->C: stats (display default character stats)
    S->C: drawinfo (display motd)
    S->C: query (get player name)
    C->S: reply (return player name)
    S->C: drawinfo (inform player to enter password)
    S->C: query (request password)
    C->S: reply (return player password.)

At this point, things could deviate two ways - player could be
starting a new character, in which case, numerous draw infos, query's
(stat rolling), replies, stats (change stats that were just
rolled), map updates (player changing class) could be sent. However,
we will assume that the player actually entered the proper password
and an existing character is rejoining the game.

Once again, I am not positive this is the correct order or not.

    S->C: player (send player object.)
    S->C: stats (send player stats)
    S->C: pixmap (assuming on different map and we haven't sent some of
            the images before)
    S->C: map (map player was saved on)
    S->C: pixmap (assuming we have not sent image for item before)
    S->C: item (item in players inventory or where he is standing)

After that is established, a loop is established that typically will result
in these commands being sent at various times:

    S->C: stats - to inform the client when stats go up or down.
    S->C: map_scroll (when the player moves)
    S->C: map (update after map_scroll, or when player changes maps.)
    S->C: pixmap/bitmap (with maps commands) to update faces.
    S->C: drawinfo (Tell about hitting creatures, applying, etc.)
    S->C: item (tell what objects are in players inventory, or space he is standing
        on.
    C->S: command (general commands, like north, fire, cast, etc.)
    C->S: apply (applying and object.)
    C->S: move (moving and object)
    C->S: examine (examine an object.)

    S->C: query (keypress for shop listing, some other areas)
    C->S: reply (from last query)

Deprecated Commands
-------------------
These are no longer used in latest versions of the server and client. In
some cases, the code may exist in either client or server in order for them
to support more different versions (so that more clients can play on a server,
or so you can use the client to play on more servers).

The reasons for them being deprecated is noted - in most cases it is because
they have been replaced by a newer command, or have become de facto defaults.

    S->C: drawinfo <color> <text>
          <color> string value of integer data
          <text> string of text message.

Tell the client to draw whatever text in color. Color are specified
in newclient.h, and is sent as a string. The client is free to do
whatever it wants with the color information (which may very well
mean ignore it.)

    C->S: toggleextendedtext <type>...
          Deprecated: Server will use drawextinfo for all types, so
          requesting this type information is no longer needed.

Ask the server to send extended text information for a given type.
type is a list of decimal integers.
Currently supported/reserved values for types are described in drawextinfo

    S->C: ExtendedTextSet <type1> <type2> .... <typen>
          Deprecated: Server will use drawextinfo for all types, so
          requesting this type information is no longer needed.

Tell client what actually are the extended infos server may
send to the client when this is needed. All those infos will
be related to the map and send through mapextended command.
Each string represent an info which is enabled. Look
at toggleextendedinfos and drawextinfo for details.

    C->S: setfacemode <val>
          Deprecated: Only one facemode (PNG) is supported. Client uses setup
          to request caching (or not)

This tells the server what type of display mode the client is using.
<val> is a plaintext integer. 0=no faces, 1=bitmap, 2=xpm (pixmap).
3=png (added in CS version 1022)
If the 5'th bit is true (ie, 0x10 & val is true), that then informs
the server that client is caching the images, and only send image
names.

    C->S: toggleextendedinfos <string1> <string2> .... <stringn>
          Deprecated: Rolled into map2 protocol command, which is standard.

Ask the server to send some additional information about the map.
This command is followed by 1 or more strings. String are separated
with spaces. Each string toggle an info. The server will respond
with the command ExtendedInfoSet telling client what actual
extended infos will be send to the client.
Valid extended infos are as follow:
    smooth
        send smoothlevel information to the client.

    S->C: ExtendedInfoSet <string1> <string2> .... <stringn>
          Deprecated: Rolled into map2 protocol command, which is standard.

Tell client what actually are the extended infos server may
send to the client when this is needed. All those infos will
be related to the map and send through mapextended command.
Each string represent an info which is enabled. Look
at toggleextendedinfos and mapextended for details.

    C->S: setsound <val>

Deprecated: Replaced with setup options
Obsolete command, should not be used, will be removed at some point.

    S->C: sound <x><y><num><type>

Deprecated: Replaced by sound2
Obsolete, will never be sent.

Deprecated Setup Options
~~~~~~~~~~~~~~~~~~~~~~~~
The setup command is still in use, but over time, many options have become
defaults. This documents those now obsolete values.

[options="autowidth,header"]
|===========================
|Command|
        Description

|exp64|
        If true, client can handle the 64 bit exp values that
	    are now used. Otherwise, values are sent as 32 bit. Setting
	    this flag also means that skill exp will be sent, and it will
	    be sent in revised method as described in the stats command.
	    Value is an integer in string format.
	    Deprecated: This is always the default on servers with protocol version >=1028.

|extendedMapInfos (0/1)|
	    Toggle sending from server of extended map informations.
	    What lies in this extended info depended on what extended
	    infos the client asked. See toggleextendedinfos command for
	    details.
        Deprecated - server will always including smoothing information
        in map2 data.

|extendedTextInfos (0/1)|
	    Toggle sending from server of extended text informations.
	    What lies in this extended info depended on what extended
	    infos the client asked. See toggleextendedtext command for details.
        Deprecated - server will always use drawextinfo

|inscribe (0/1)|
	    Client will probably always send 1. Server will reply with 1 if it
	    supports the 'inscribe' command, 0 else.
        Deprecated - client should presume all servers support this

|newmapcmd (0/1)|
	    This tells the server if the client understands the newmap
	    protocol command. This is used by the client in the fog
	    of war mode to receive newmap commands from the server each time
	    the player changes maps.
        Deprecated - server will assume clients support newmapcmd

|sound (bitmask)|
	    Obsolete, server will return FALSE.
        Deprecated - replaced with sound2 setup command.
|===========================

Programming Notes
-----------------
These are a few quick notes on how things work. Note that they really
only apply to the code in the standard distribution, most of the direct
i/o is handled by functions that are talked about. If writing a client
from scratch, you will need to port this over (or write your own - it
isn't very complicated.)

For the server and the C client, a SockList structure is used for basic
data handling. Basically, this is just a structure that has an unsigned
character buffer and a length field (which contains the length of data in
the buffer, not the actual buffer length.)

As a side note, when sending a packet, you can supply the length of the
data and the sending routines will take care of sending the 2 bytes of
length information.

When getting a packet, these 2 bytes are at the start of the buffer and
not removed.

In the client, there is a file called newsocket.c - except for the
SockList data type, it could probably be used by itself. The
newsocket.c file contains some routines to pack ints, shorts, and
single chars into SockList structs, as well as functions for the
reverse. It also contains a function to send socklists, as well as
read them. The Add??? functions increase the len field of the
socklist, the Get??? functions do not change the pointer in anyway.
Thus, to get an int and move the buffer, you do something like:

   int = GetIntString(data); data+=4

As a side note, if you malloc the data for the buffer, make sure to free
it when done.

There is also the newclient.h file which is shared between the client and
server. This file contains the definition of the SockList, as well as
many defined values for constants of varying means (ie, that in the
stats command, a stat value of 1 is hit points, etc.)  When porting to
a new system, you will need to grab these constant values for yourself.
Many of the constants in this file are used in the protocol to denote
types.

Image Caching
~~~~~~~~~~~~~
Image caching has been implemented on the client, with necessary server
support to handle it. This section will briefly describe how image
caching works on the protocol level, as well as how the current client does
it.

First, the client checks for an option denoting the image caching
is desired. If so, we initialize all the images to a default value - this
means we don't need to put special checks into the drawing code to see if
we have an image - we just draw the default images (I use a question mark
pixmap, since that makes it very easy to see what stuff is cached.)  We
also initialize an array which will hold the number to name mapping so
that when we actually get the image, we know what filename to store it
as.

Second, we request the server to do image caching. This is done
by or-ing the cache directive to the image mode we want.

    C->S: setup facecache 1

Then, when the server finds an image number that it has not send to the
client, it sends us a name command information us the number to name mapping:

    S->C: face2 65 1 5264 CSword.115

Note that this is not exactly how the data is sent - the numbers are
actually sent in binary form, and there is no space between that the
and the name. Such formating is difficult here, but the above example
illustrates the data is sent.

The client then checks for the existence of the image locally. It is
up to the client to organize images appropriately (based on name,
faceset, etc). The current client stores images in
~/.crossfire/images, and then splits them into sub directories based
on the first 2 letters - in the above example, the file would be
~/.crossfire/images/CS/CSword.115

If the client does not have the image or otherwise needs a copy from the
server, it then requests it:

    C->S: askface 65

The server will then send the image via image2 protocol commands.

    S->C:  image2 <face><set><len><data>

Because image2 does not include the image name, the client must store
the name & number mapping someplace before sending the askface. In
the C client, this is done by using an array of character pointers, so
then in position 65, we do a strdup of the name, store it, then use it
when the pixmap/bitmap command comes in, and free that data.

Also, the client does occasional redraws of all data if it has received
new images and is running in cached mode. Otherwise, the map can remain
out of date indefinitely (although, once the player moves, things will get
redrawn.)

This has the effect that first time running in cached mode, performance
will actually be a little bit worse for the client (after all, it needs
to still request all the images, but is still doing pretty constant redraws
of the data.)  But times after that, performance is greatly improved.

Changes
-------
This area documents changes in the protocol version and what happened between
them. Note that this is not a complete list, as the setup command
is used to control many cases.:

Client
~~~~~~
CS version 1022 -> 1023: just to sync version with server

CS version 1021 -> 1022: Client supports sending of verbal image type
questions.

Server
~~~~~~
SC version 1022 -> 1023: Server supports sending png images (addition of
image command).

SC version 1023 -> 1024: Server will send two part names (described in
item command) which contains the singular & plural form of the name)

SC version 1024 -> 1025: Support for sending all resistance
values in the stats command.

SC version 1025 -> 1026: Add face1 command that includes the image
checksum.

SC version 1026 -> 1027: Add requestinfo/replyinfo commands - client
can check this to know if it should expect a replyinfo to its requestinfo.

SC version 1027 -> 1028: mostly remove obsolete commands:
 image, face, face1, map, map1, map1a, command

SC version 1028 -> 1029: Changes the way weapon_speed is reported for
  the player - version 1028 needed the client to divide weapon speed
  by player speed to get actual value, version 1029 just reports weapon
  speed as it should be displayed.

Todo
----
It probably makes more sense to do a more preemptive handling of socket
events. That is, instead of sleeping 120 ms, then checking all the
sockets, we do a select on all the file descriptors with an appropriate
sleep time.

If we get input, we handle it at that time if the player has an action. In
this way, instead of handling all the actions after sleeping for the 120ms,
we can instead spread them out more. Only when the 120ms expire do we
then do all the actions like move the monsters, regenerate HP, etc.

The only potential problem I see with this right now is that select will
return immediately if there is data on the socket (player has used up all
their time, are paralyzed, etc.)  This would probably mean that the server
needs to do internal buffering, which complicates things some. The
potential advantage with this is that we could peek at the data, and
if the command is not a player action (ie, maybe requesting an image, or
a misc command like who), we could still execute it. Actually, we can
get around the select problem by only adding the file descriptors from
sockets that actually have time to perform actions.
