public static extern int recvfrom(
     int s,
     byte[] buf,
     int len,
     int flags,
     ref SockAddr_In from,
     int fromlen);
 public static extern int sendto(
     int s,
     byte[] buf,
     int len,
     int flags,
     ref SockAddr_In to,
     int tolen
     );
 public static extern int bind(int s, ref SockAddr_In name, int namelen);
 public static extern int connect(
     int socket,
     ref SockAddr_In name,
     int namelen
     );