svctcp_create() creates a TCP/IP-based RPC service transport,
to which it returns a pointer. The transport is associated with the socket
sock, which may be
which case a new socket is created. If the socket is not bound to a local TCP
port, then this routine binds it to an arbitrary port. Upon completion,
xprt->xp_sock is the transport's socket descriptor,
xprt->xp_port is the transport's port number. Since
TCP-based RPC uses buffered I/O, users may specify the size of buffers;
values of zero choose suitable defaults.
svctcp_create() returns NULL if it fails, or a pointer to the RPC service transport otherwise.