hi u all
I want to program an application which sends or receives a file. I can program for client/server but when i want p2p it seems difficult because there should be freedom in initiating the connection. One side will not be dedicately responsible for listening incomming connections and the other for initiating the connection in the case of p2p. I want to program it in C++/CLI by using System::Net.

can any one give me some hint
yours solomon

Every single p2p program I know of uses some kind of server to initiate protocol (like trackers in bittorrent), most of the time the servers are a different entity from the peers that will end up sharing the information.
Even in VoIP calls, each peer know only the address of the proxy server they are registered to and this servers are the ones that initiate communications.
In you specific case, it could be possible to use UDP and send messages to a specific port, however each peer need to fully know the other peer, and that will limit you application.
I believe that using a server that is not either peer should solve a lot of problems, but I don't know if it is possible.