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I've seen a lot of answers here that say to use close() to destroy a socket but the guide I used from msdn has me using closesocket(). I'm wondering if there is a difference and if there are reasons to use one or the other.
In both cases, I am seeing the suggestion to use shutdown() so that's all well and good.
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close () is a *nix function. It will work on any file descriptor, and sockets in *nix are an example of a file descriptor, so it would correctly close sockets as well. closesocket () is a Windows-specific function, which works specifically with sockets.
The semantics of the closesocket function are affected by the socket options that set members of linger structure. If the l_onoff member of the LINGER structure is zero on a stream socket, the closesocket call will return immediately and does not receive WSAEWOULDBLOCK whether the socket is blocking or nonblocking.
The (blocking) Windows Socket 1.1 call was canceled through WSACancelBlockingCall . The socket is marked as nonblocking, but the l_onoff member of the linger structure is set to nonzero and the l_linger member of the linger structure is set to a nonzero timeout value. The closesocket function closes a socket.
The closesocket function closes an existing socket. A descriptor identifying the socket to close. If no error occurs, closesocket returns zero. Otherwise, a value of SOCKET_ERROR is returned, and a specific error code can be retrieved by calling WSAGetLastError. A successful WSAStartup call must occur before using this function.
close() is a *nix function. It will work on any file descriptor, and sockets in *nix are an example of a file descriptor, so it would correctly close sockets as well.
closesocket() is a Windows-specific function, which works specifically with sockets. Sockets on Windows do not use *nix-style file descriptors, socket() returns a handle to a kernel object instead, so it must be closed with closesocket().
I find it rather shameful that BSD-sockets do not include specific counterpart to socket function, which could be used anywhere - but such is life.
The last, but not the least, do not confuse shutdown'ing a socket with closing the socket. shutdown() stops transmission on a socket, but the socket remains in the system and all resources associated with it remain. You still need to close the socket after shutting it down.
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