Comunicating with server

Ok so I got pretty decent at java and made a simple msn messenger copy using GUI. Now the only problem is that each time when you write it reads off and writes into the text file that is located at the same computer, so the only way it works if the two people are sharing the comp. But lets say I want to make it so that my application connects to the website(I have a web) and reads the .txt file that is located in there. Is there any tutorials I can look up on how to do that, or am I supposed to look at a specific java class.
Just directing me to a class would be a great help, and any further assistance would be greatly apreciated.
Thanks a lot in advance to all who help.

Use servlets+sockets etc