int nng_close(nng_socket s);
nng_close() function closes the supplied socket, s.
Messages that have been submitted for sending may be flushed or delivered,
depending upon the transport.
Further attempts to use the socket after this call returns will result
Threads waiting for operations on the socket when this
call is executed may also return with an
Closing the socket while data is in transmission will likely lead to loss
of that data.
There is no automatic linger or flush to ensure that the socket send buffers
have completely transmitted.
It is recommended to wait a brief period after calling
nng_send() or similar functions, before calling this
This function returns 0 on success, and non-zero otherwise.
The socket s is already closed or was never opened.