How to manager control sockets and transfer sockets?

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http://stackoverflow.com – We are developing a network application based on C/S, in this application the server needs to transfer files to clients and sometimes receive files from clients. So in the server application, for every client it needs to create a control socket and many transfer sockets. My question is how we can create and define a socket as role of control socket or transfer socket? ( below are deleted: And how can the server application distinguish between the control socket and the transfer sockets? ). Currently the servers use a listening socket, and for all new connections established by accept(listeni (HowTos)