3-rd party component for file transferring via sockets - Java

I study computer-science and right now I am in a middle of Networking course. I need to develop a开发者_高级运维 simple FTP program (client + server). The server listens to port X and waits to connection request. Every client has it's own thread. The server send the client the current list of files it has. The client ask for file and in that point I need to open new socket for the file transferring. When half of the file was sent the client need to take a decision if he wants the rest of the file - at that time the server waits for the client's decision.

Although it seems a little problem and although I did chat programs based on TCP and UDP on the previous courses I got stuck.

I search for 3-rd party component that simplify the file transferring.

Thank You, Oz

Common IO has a lot of nice utilities to deal with files and sockets.