C++ application: Is it possible to pass accepted TCP connection from one process to another?

Question

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.

Nam

Answer 1

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.

Morrie

Is there any library that is alike libancillary for windows? and are out there any code samples / examples on how to do such thing on windows? – Nam

Don't know of any library - The only time I had to do this I just wrote it from scratch. See msdn.microsoft.com/en-us/library/ms740478%28v=vs.85%29.aspx – Morrie

So.. I tried to create a sample using Boost.ASIO and Windows WSADuplicateSocket... Currently at least inside one process #5327064 may be you could posibly take a look and provide any help? Pleeease) – Nam

Answer 2

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.

The

what does it mean? that two processes will share same connection? – Kermes

@Andrey: yes, so they must co-ordinate their access to the connection. – The

@Andry - A socket is just a file descriptor. Once you accept() a connection, you can do whatever you want with it, including sending it to another local process. – Scutch

A socket is not a file descriptor on Windows. – Devine