VMS Help TCPIP Services, Programming Interfaces, Sockets API, listen(), Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    This function creates a queue for pending connection requests
    on socket s with a maximum size equal to the value of backlog.
    Connections can then be accepted with the accept() function.
    If a connection request arrives with the queue full (that is,
    more connections pending than specified by the backlog argument),
    the request is ignored so that TCP retries can succeed. If the
    backlog has not cleared by the time TCP times out, the connect()
    function fails with an errno indication of ETIMEDOUT.
    Related Functions
    See also accept(), connect(),  and socket().