VMS Help TCPIP Services, Programming Interfaces, RPC Server Routines, svctcp_create, Arguments  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 sock
    The socket with which the connection is associated. If sock is
    RPC_ANYSOCK, then this routine opens a new socket and sets sock.
    If the socket is not bound to a local TCP port, then this routine
    binds it to an arbitrary port.
 sendsize
    The size of the send buffer. If you specify 0, the routine
    chooses a suitable default.
 recvsize
    The size of the receive buffer. If you specify 0, the routine
    chooses a suitable default.