creating a chat application

I am an undergrad Computer Science student working with a company as part of my education. My boss wants me to investigate what it would take to implement text chat into one of our applications. The problem is I know nothing about network programming, or even where to start on this. The good news is the application we want to add this functionality to is a VoIP voice communication application that can make unicast and multicast calls, so the program is already capable of connecting to the internet and can send and receive packets from other users. I could probably modify the gui interface to include a textfield you can type into and send to one of your contacts, but I just don't know a thing about network programming, or socket programming, and how you would break the data up into packets and set it accross, or whatever.

So if someone can just point me in the right direction and tell me what it is i need to know about to do this, and where I could best learn it, I would very much appreciate that!

Not sure what kind of tools you have.
If you want to know how to sending/receiving data through network,
you need to read some books about network programming first.

Theres no other place to begin than beej's guide:
http://beej.us/guide/bgnet/

Afterwards you can browse the codeproject website for some examples. If the program is for Windows then you'll most definitely need to take a look at the MSDN documentations as a resource.

regards,
blaquee