WinsockUDP + recv() + MSG_PEEK = WSAEMSGSIZE

[MikeAThon]

Here's another example of packet-type identification, which is based on a union. I found the example at http://www.gamedev.net/community/for...sp?forum_id=15. In general, if you have not been there already, you really should visit and search over at the www.gamedev.net site, since you're writing a game:

  struct PlayerPosPacket {
    unsigned short code;
    unsigned short player;
    float pos_x, pos_y, pos_z;
    float vel_x, vel_y, vel_z;
    float heading;
  };

  PlayerPosPacket packet;
  packet.code = PLAYER_POS;
  packet.player = thePlayerId;
  ...
  int r = sendto( sock, (char const *)&packet, sizeof(packet), 0, (sockaddr *)&dst_addr, sizeof(dst_addr) );
  if( r < 0 ) { error(sock); }

  union {
    PlayerPosPacket playerPos;
    SomeOtherKindOfPacket someOther;
  } recvPacket;

  int r = recvfrom( sock, (char *)&recvPacket, sizeof( recvPacket ), 0, (sockaddr *)&src_addr, sizeof(src_addr) );
  if( r < 0 ) { error(sock); }
  /* assume all packet types start with unsigned short code; */
  switch( recvPacket.playerPos.code ) {
    case PLAYER_POS:
      if( r != sizeof(recvPacket.playerPos) ) { formatError(); }
      do_playerPos( recvPacket.playerPos, src_addr );
      break;
    case SOME_OTHER:
      if( r != sizeof(recvPacket.someOther) ) { formatError(); }
      do_someOther( recvPacket.someOther, src_addr );
      break;
    ...
  }

Mike