StackOverflow2013

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POStrange/unexplainable behaviour of Eclipse and multicast packets
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copied!<p>I have a very similar behaviour as described <a href="https://stackoverflow.com/questions/1264948/link-scope-ipv6-multicast-packets-suddenly-not-routable-on-a-macbook-pro">here</a>:</p> <ul> <li>running on a Mac Book Pro, Snow Leopard</li> <li>using Multicast Sockets to send and receive packets on localhost</li> </ul> <p>I'm using Eclipse and observed the following behaviour when the client / server are started from within the workspace:</p> <ul> <li>if the wireless interface (airport) is up and running, the client does <em>not</em> receive any packets</li> <li>if the interface is turned off, everything works as expected</li> </ul> <p>But what I don't understand is:</p> <ul> <li>if I create a JAR and run the code in any console -> all good! Just Eclipse seems not to like airport ;-)</li> <li>depending on what wireless network I'm connected to, the above behaviour might change, i.e. it also works if airport is enabled (for example @ Uni)</li> </ul> <p>Does anyone have an idea 'bout this?</p> <p>Cheers</p> <p>Below the straightforward code for server / client:</p> <pre><code>@Override public void run() { String multicastAddress = "224.0.0.2"; int multicastPort = 8000; MulticastSocket socket = null; try { try { InetAddress multicastGoup = InetAddress.getByName(multicastAddress); socket = new MulticastSocket(multicastPort); socket.joinGroup(multicastGoup); } catch (IOException e) { e.printStackTrace(); return; } byte[] buffer = new byte[1024]; while (true) { DatagramPacket packet = new DatagramPacket(buffer, buffer.length); System.out.println("BEFORE RECEIVE: listening on " + multicastAddress + ":" + multicastPort); socket.receive(packet); System.out.println("PACKET RECEIVED"); System.err.println("Client received: " + new String(packet.getData())); } } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } finally { socket.close(); } } </code></pre> <p>Server:</p> <pre><code> public void run() { MulticastSocket socket = null; try { String multicastAddress = "224.0.0.2"; int multicastPort = 8000; InetAddress multicastGoup = InetAddress.getByName(multicastAddress ); socket = new MulticastSocket(multicastPort); socket.joinGroup(multicastGoup); byte[] data = new String("Teststring").getBytes(); while (true) { socket.send(new DatagramPacket(data, data.length, multicastGoup, multicastPort)); System.out.println("SERVER: Datagram sent"); Thread.sleep(1000); } } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } finally { socket.close(); } } </code></pre>

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