Returns the socket device's OpenVMS I/O channel (SDC) associated
    with a socket descriptor.
    Format
      #include  <socket.h>
      short int decc$get_sdc  ( int s );

1  –  Argument

 s
    A socket descriptor.

2  –  Description

    This function returns the SDC associated with a socket. Normally,
    socket descriptors are used either as file descriptors or with
    one of the functions that takes an explicit socket descriptor
    as its argument. Sockets are implemented using TCP/IP device
    sockets. This function returns the SDC used by a given socket
    descriptor so you can directly access the TCP/IP facilities by
    means of $QIO system services.

3  –  Return Values

    0                  Indicates that s is not an open socket
                       descriptor.
    x                  The SDC number.