help : file transfer using sockets???

can someone explain me how i cud transfer files from client to server & from server to client using tcp sockets.

if any1 has worked on the same thing ... cud u tell me how u did it ..

also if assuming both my client and server are on same machine and i have just one card ... i will have just one ip address ... so if i require a server to be connected to random number of clients ... how wud i do it ... i know port numbers cud be used .. but without hardcoding the port numbers ... how wud i assign port numbers for each connection?

thanks a lot

aseem