Capture other Messenger's messages?

Hi,
I am very new to Network programming. My task is to capture messages from the port of another messenger presently working in our LAN, which is not a Server-Client based.
Presently, it is using port 4000 for messages. I need to develop another application (I'm gonna use Vb.Net) which would be able to communite with this existing Messenger as well as working on its own..

Please suggest some code / methods /ideas, would be really appreciated.

Thanks
Farrukh

you need to understand the program's Message protocol.

There are basically two ways in doing this:

1. If the Messenger Protocol is freeware or is opensource then you should have no problem in finding the documentation on the protocol...

2. Otherwise you can monitor the packets being send to and from two devices and then make a program from what you have learned. Although this way is more time consuming and difficult its better because then you really understand the Protocol...


Raw Winsock Packet Sniffer (freeware):
http://www.softpedia.com/get/Network...-Sniffer.shtml

Quote:

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Originally Posted by Tommy101

you need to understand the program's Message protocol.

There are basically two ways in doing this:

1. If the Messenger Protocol is freeware or is opensource then you should have no problem in finding the documentation on the protocol...

2. Otherwise you can monitor the packets being send to and from two devices and then make a program from what you have learned. Although this way is more time consuming and difficult its better because then you really understand the Protocol...


Raw Winsock Packet Sniffer (freeware):
http://www.softpedia.com/get/Network...-Sniffer.shtml

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Thanks a lot Tommy for such a useful information :)
I am looking into this.

If there is any code examples, kindly let me know.

thanks
Farrukh