Accepts a connection on a passive socket.
    The $QIO equivalent is the IO$_ACCESS system service with the
    IO$M_ACCEPT modifier.
    Format
      #include  <types.h>
      #include  <socket.h>
      int accept  ( int s, struct sockaddr *addr, int *addrlen );
                  (_DECC_V4_SOURCE)
      int accept  ( int s, struct sockaddr *addr, size_t *addrlen );
                  (not_DECC_V4_SOURCE)

1  –  Arguments

 s
    A socket descriptor returned by socket(), subsequently bound to
    an address with bind(), which is listening for connections after
    a listen().
 addr
    A result argument filled in with the address of the connecting
    entity, as known to the TCP/IP kernel. The exact format of the
    structure to which the address parameter points is determined by
    the address family. Specify either the IPv4 address family (AF_
    INET) or the IPv6 address family (AF_INET6).
 addrlen
    A value/result argument. It should initially contain the size of
    the structure pointed to by addr. On return it will contain the
    actual length, in bytes, of the sockaddr structure that has been
    filled in by the TCP/IP kernel.

2  –  Description

    This function completes the first connection on the queue
    of pending connections, creates a new socket with the same
    properties as s, and allocates and returns a new descriptor
    for the socket. If no pending connections are present on the
    queue and the socket is not marked as nonblocking, accept()
    blocks the caller until a connection request is present. If the
    socket is marked nonblocking by using a setsockopt() call and no
    pending connections are present on the queue, accept() returns
    an error. You cannot use the accepted socket to accept subsequent
    connections. The original socket s remains open (listening) for
    other connection requests. This call is used with connection-
    based socket types (SOCK_STREAM).
    You can select a socket for the purposes of performing an accept
    by selecting it for a read.
    Related Functions
    See also bind(), connect(),  listen(), select(), and socket().

3  –  Return Values

    x                  A positive integer that is a descriptor for
                       the accepted socket.
    -1                 Error; errno is set to indicate the error.

4  –  Errors

    EBADF              The socket descriptor is invalid.
    ECONNABORTED       A connection has been aborted.
    EFAULT             The addr argument is not in a writable part of
                       the user address space.
    EINTR              The accept() function was interrupted by a
                       signal before a valid connection arrived.
    EINVAL             The socket is not accepting connections.
    EMFILE             There are too many open file descriptors.
    ENFILE             The maximum number of file descriptors in the
                       system is already open.
    ENETDOWN           TCP/IP Services was not started.
    ENOBUFS            The system has insufficient resources to
                       complete the call.
    ENOMEM             The system was unable to allocate kernel
                       memory.
    ENOTSOCK           The socket descriptor is invalid.
    EOPNOTSUPP         The reference socket is not of type SOCK_
                       STREAM.
    EPROTO             A protocol error occurred.
    EWOULDBLOCK        The socket is marked nonblocking, and no
                       connections are present to be accepted.