MSN Messenger Protocol (Practical Implementation)

a.k.a

How to make your own version of MSN messenger



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Check out how to make your own yahoo messenger by going here yahoo.htm

You have been using MSN for quite some time wondering how it works. Well You need not look any further. This article will not just tell you how MSN works but will also tell you how to make your own version of MSN messenger. You can download a sample application from here Unify.zip .All the dll's required for the program to run are also in the sample code.Let's get ready to rumble!!!!

 

We can split up the working of MSN messenger into 2 phases

 

The Authentication Phase involves logging into the MSN messenger server and also (friends) list retrieval in this case.

The Instant Messaging Phase involves sending/accepting requests for an Instant Messaging session and also sending/receiving messages.

 

The MSN messenger protocol is an ASCII based protocol. In other words the commands are in pure English !!!.The first phase involves connecting to an MSN messenger server .In this case we shall connect to the server 64.4.13.58 on port 1863(MSN messenger works through port 1863).

Once the connection is done we need to start the log in process. The first stage in this phase is the versioning stage. In this stage the client (in this case your app) lists/sends the versions that it can support to the server and waits for the server to respond.

VER 0 MSNP5 MSNP4 CVRO

In the MSN messenger protocol a "trial id" is sent along with every command. The trial id starts from 0 and is incremented every time the server responds successfully to the client's commands.

 

The server responds like this

VER 0 MSNP5 MSNP4

The Client and the server have agreed on a version in which they will communicate.

 

Next the client sends a request to the server asking it for the name of the security package it supports for authentication.

INF 1

Unlike Yahoo, Rediff and a few other Messengers MSN does not actually send the password as it is.It encrypts the password while sending it ensuring that your password will not be leaked out easily if somebody monitors your port.

 

The server responds with this

INF 1 MD5

Here MD5 is the name of the security package which the server currently supports.

Next the client sends the userid to the server

 

USR 2  MD5  I  venky_dude@hotmail.com

Here the server does a check whether it contains all the relevant details about the user for authentication .If it does not then it sends the following reply

 XFR 2  NS 64.4.13.55:1863  0

What the server says is that the client should connect to the Notification Server(NS) on 64.4.13.55 on port 1863. We close the current connection and repeat the  steps while being connected to the new server i.e  64.4.13.55

Now the server to which we are connected to has the relevant information about the user trying to log in. The server replies this way

USR 5  MD5  S 989048851.1851137130

 The string which is sent by the server is the " MD5 Hash". It is a hash generated by the server and is used in the authentication process. The client then has to send the password which is encrypted using the MD5 algorithm.In effect the client has to send the unique MD5 equivalent of the MD5 hash i.e 989048851.1851137130 in this case and the password combined .i.e. MD5 equivalent of (hash+pass). In this case it turns out to be 3b7926d277068ec49576a0c40598ff21.

USR 6 MD5 S 3b7926d277068ec49576a0c40598ff21

If the password is right then the server replies with this

USR 6 OK venky_dude@hotmail.com venkat

Here the last word is the nickname/name by which the user is known.

Now we are logged into the server but our status is still offline. We need to change our status to online in order to send and receive messages. The client does this in the following way

CHG 7 NLN

The server replies with some details about emails in the account and also friends who are online.

CHG 7 NLN
MSG Hotmail Hotmail 221
MIME-Version: 1.0
Content-Type: text/x-msmsgsinitialemailnotification; charset=UTF-8

Inbox-Unread: 2
Folders-Unread: 0
Inbox-URL: /cgi-bin/HoTMaiL
Folders-URL: /cgi-bin/folders
Post-URL: http://www.hotmail.com

To get a list of people who are in our friends list we may send this command

LST 8 RL

The server responds this way

LST 8 RL 69 1 19 venky_dude@hotmail.com venkat
LST 8 RL 69 2 19 puxxxxx@hotmail.com PUJA
LST 8 RL 69 3 19 vancxxxxx@hotmail.com ramachandran
LST 8 RL 69 4 19 moxxxxx@hotmail.com chandramouli
LST 8 RL 69 5 19 v_n_xxxxx@hotmail.com Narayanaswamy
LST 8 RL 69 6 19 dexxxxx@hotmail.com Venkatesh
LST 8 RL 69 7 19 lousydxxxxx@hotmail.com deepika%20kalyani%20Vairam 
LST 8 RL 69 8 19 hexxxxxr@hotmail.com Hetchar%20Ramachandran
LST 8 RL 69 9 19 ambxxxxx@hotmail.com Aiyer
LST 8 RL 69 10 19 suxxx@hotmail.com Ganesh
LST 8 RL 69 11 19 deexxxxx@hotmail.com Deepak
LST 8 RL 69 12 19 anilxxxxx@hotmail.com anil
LST 8 RL 69 13 19 dixxxxx@hotmail.com
LST 8 RL 69 14 19 nvxxxx@hotmail.com giri
LST 8 RL 69 15 19 shxxx@hotmail.com Hari
LST 8 RL 69 16 19 radhikashuxxxxx@hotmail.com radhika
LST 8 RL 69 17 19 eskaxxxxx@hotmail.com kannan
LST 8 RL 69 18 19 shaxxxxx@hotmail.com Shankar
LST 8 RL 69 19 19 puneetagarxxxxx@hotmail.com puneet

 

 

*Every time a friend comes online the server(NS) sends us the following command

NLN 9 NLN deaxxxx@hotmail.com Venkatesh

and when the friend goes offline the server sends us this

FLN 9 FLN deaxxxx@hotmail.com

 

We have successfully logged into the MSN Messenger server. The Instant Messaging phase is next.

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