Cocoa AsyncUDPSocket framework, (long)tag variable explanation and my delegate only sometimes called.

Question

Hello Community,

my first post and also my first question. I am currently playing around with the Artnet protokoll, which is based on UDP. Trying to develop an Cocoa Application that reads Artnet data. I decided to use the AsyncUDPSocket Cocoa framework and got it working somehow.. So when i try to send a packet to my listen port using

nc -u localhost 6454

my delegate gets called. If i try this with another Artnet application my delegate never gets called back, but i can see the packets in the packet analyzer..

I suspect it must be something caused by the "tag". Can someone explain the (long)tag variable as i can find no Documentation about this Value and i can find no answer on the net. Also i might add i am relatively new to cocoa developing so maybe it´s a very basic error..

below is my init code for the sockets:

 listenSocket_unicast = [[AsyncUdpSocket alloc] initWithDelegate:self];  // This one is not added to the Autorelease pool, so cocoa doesnt delete my socket object.
 listenSocket_broadcast = [[AsyncUdpSocket alloc] initWithDelegate:self];  // This one is not added to the Autorelease pool, so cocoa doesnt delete my socket object.

 // Bind unicast socket..if adress is not the loopback device

 if (![SocketAddress isEqualToString:@LOOPBACK])
 if ([listenSocket_unicast bindToAddress:SocketAddress port:ARTNET_PORT error:nil] == NO)
  {
  NSLog (@"Could not bind unicast socket on Adress %@ and port %i",SocketAddress, ARTNET_PORT);
  return NO;
  }
 else  NSLog (@"Unicast Socket bind to on Adress %@ and port %i",SocketAddress, ARTNET_PORT);
 // Bind broadcast socket..
 if ([listenSocket_broadcast bindToAddress:SocketBroadcastAdress port:ARTNET_PORT error:nil] == NO)
  {
  NSLog (@"Could not bind broadcast socket on Adress %@ and port %i",SocketBroadcastAdress, ARTNET_PORT);
  return NO;
  }
 else
  NSLog (@"Broadcast Socket bind to on Adress %@ and port %i",SocketBroadcastAdress, ARTNET_PORT);




 [listenSocket_unicast receiveWithTimeout:-1 tag:0];
 [listenSocket_broadcast receiveWithTimeout:-1 tag:0];

 [listenSocket_broadcast enableBroadcast:YES error:nil];

and the code i currently try to get working:

    -(BOOL)onUdpSocket:(AsyncUdpSocket *)sock didReceiveData:(NSData *)data withTag:(long)tag fromHost:(NSString *)host port:(UInt16)port
{
 [sock receiveWithTimeout:-1 tag:0];
 NSLog (@"UDP Delegate executed");
 return YES;
}

Thanks in advance,

matthias

Answer 1

The problem was i did not call the Read method at first.. so the reading never started.

Answer 2

Glad you found your problem, but to actually answer your question about the tag variable, it's simply a way to track messages. The tag is not sent with the messages, but when a response comes to it, that will have the same tag, so you can organize them. If you don't need to do that sort of thing, just leave tag as 0 and you can ignore it.