The J-Lan Communicator 1.2 Protocol
-----------------------------------

The first objective of the protocol is to fit in the KISS concept: Keep It
Simple, Stupid.

jlanc uses UDP packets with little headers of 4 or 5 ASCII characters followed
of command data (if applicable), altogether bound in a String.

jlanc protocol relies in UDP broadcasting and doesn't need a central server,
and new clients can join/part easily.

This document is provided in order to allow the development of third party
clients. Notice this information is provided "AS IS" and the protocol
eventually may change in next releases of the program.

You may send comments and/or ideas to:

	Juan J. Martinez <reidrac at usebox.net>

History
-------

2003/10/29 version 1.2
2003/07/27 version 1.1
2003/07/13 version 1.0

Command list
------------

/HLO name

	name: local user name
              from 1 to 16 of any character but '@', spaces at the begining
              are removed
	 dst: bcast address
	desc: this cmd is sent every time a new client joins
	      an ACK reply is spected

/BYE
	 dst: bcast address
	desc: this cmd is sent when a client leaves

/ACK name

	name: local user name
              from 1 to 16 of any character but '@', spaces at the begining
              are removed
	 dst: ip address of HLO origin
	desc: this is the reply to a HLO cmd
	      it's like a HLO cmd, but no reply is spected

/MSG data

	data: message
	 dst: bcast address
	desc: this is a text message sent to all the users

/PRV data

	data: message
	 dst: ip address of certain user
	desc: this allows to send a 'private' message to just one user
	      it's like MSG cmd, but using an ip addr instead a bcast addr

/AKA name

        name: nick alias for this user
              from 1 to 16 of any character but '@', spaces at the begining
              are removed
         dst: bcast address
        desc: this cmd changes the name of this user in the network
              (aka: also known as), no reply is spected


Encryption in J-Lan Communicator
--------------------------------

/BLF data

        data: blowfish ciphered message
	 dst: ip address of certain user
	desc: sends a private message ciphered with blowfish algorithm
	      it's just like PRV cmd, but data is sent ciphered in
              base64 form (check RFC 2045).
	      
  The transformation is: Blowfish/CBC/PKCS5Padding
  The init vector is: { -45, 66, -121, -4, 91, 71, 88, 118 }

About keys in jlanc

  The key to use in BLF cmd is the byte array of the MD5 of a string provided
  by the user. The string must be the same in both clients in order to
  decrypt the message. Notice there's no method to see if the message
  is deciphered in the right way, so a wrong key should make jlanc print
  garbage in the output text area in case the data can be decrypted.


$Id: jlanc-protocol.txt,v 1.5 2003/10/29 10:16:57 reidrac Exp reidrac $
** EOF **