int nng_pipe_close(nng_pipe p);
nng_pipe_close() function closes the supplied pipe, p.
Messages that have been submitted for sending may be flushed or delivered,
depending upon the transport.
Further attempts to use the pipe after this call returns will result
|Pipes are automatically closed when their creator closes, or when the remote peer closes the underlying connection.
This function returns 0 on success, and non-zero otherwise.
The pipe p is already closed or was never opened.