The IO$_DEACCESS function closes a connection and deletes a
    socket. Any pending messages queued for transmission are sent
    before tearing down the connection.
    When used with the IO$M_SHUTDOWN function modifier, the IO$_
    DEACCESS function shuts down all or part of a bidirectional
    connection on a socket. Use the p4 argument to specify the
    disposition of pending I/O operations on the socket.
    You can specify a wait time or time-to-linger socket parameter
    (TCPIP$C_LINGER option) for transmission completion before
    disconnecting the connection. Use the IO$_SETMODE function to
    set and clear the TCPIP$C_LINGER option.
    If you set the TCPIP$C_LINGER option, a $QIO call that uses the
    IO$_DEACCESS function allows data queued to the socket to arrive
    at the destination. The system is blocked until data arrives at
    the remote socket. The socket data structure remains open for the
    duration of the TCP idle time interval.
    If you do not set the TCPIP$C_LINGER option (option is set to 0),
    a $QIO call that uses the IO$_DEACCESS function discards any data
    queued to the socket and deallocates the socket data structure.
                                   NOTE
       For compatibility with UNIX, TCP/IP Services forces a time
       to linger of 2 minutes on TCP stream sockets.
    Related Functions
    The equivalent Sockets API functions are close() and shutdown().