So I wonder - is it possible to pass accepted TCP connection (on Windows or Unix like OS) from one process to another? Here the point is to pass connection - not data in a way a proxy app would.
On Windows, use WSADuplicateSocket, pass the filled in WSAPROTOCOL_INFO to the other process, use WSPSocket to recreate a socket.
On unix-like OS'es this is possible using the sendmsg() system call. libancillary abstracts this for you.
In Unix, a TCP connection is represented as a socket file descriptor. When you fork a process, the file descriptors are inherited by the child process, including TCP sockets. (Though they may be closed on exec if given the FD_CLOEXEC flag with fcntl.)
It's also possible to transfer file descriptors between unrelated processes using a local (Unix) domain socket; see this question.
I'm not sure about Windows.
来源：https://stackoverflow.com/questions/5312773/c-application-is-it-possible-to-pass-accepted-tcp-connection-from-one-process