sin.sin_family=AF_INET;

  sin.sin_addr.s_addr=0;

  for (;;) {

       sin.sin_port=htons(alport);

       if (bind(s,(LPSOCKADDR)&sin, sizeof(sin))=0) {

              /* it worked */

       }

       if (GetLastError()!=WSAEADDRINUSE) {

              /* fail */

       }

       alport-;

       if (alport=IPPORT_RESERVED/2) {

              /* fail－all unassigned reserved ports are */

              /* in use. */

       }