[jboss-jira] [JBoss JIRA] Reopened: (JGRP-777) Revisit multicast socket creation code

[Bela Ban (JIRA)]

     [ https://jira.jboss.org/jira/browse/JGRP-777?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Bela Ban reopened JGRP-777:
---------------------------



need to backport this to 2.6.5

> Revisit multicast socket creation code
> --------------------------------------
>
>                 Key: JGRP-777
>                 URL: https://jira.jboss.org/jira/browse/JGRP-777
>             Project: JGroups
>          Issue Type: Task
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 2.6.5, 2.7
>
>
> [Dieter Cailliau]
> I looked into the UDP class (trunk) and found out that the MulticastSocket(port) constructor is used.
> This doesn't work well on many linux systems: http://forum.java.sun.com/thread.jspa?threadID=5216130&messageID=9875372 It's not entirely clear who's 'fault' this is, but i have a workaround below.
> I experienced this problem in jgroups when i tried to set up 2 distinct processes on the same machine, that use a different stack with different UDP mcast_addr. Still the one process would complain about the other: discard msg from different group.
> java 1.5.0_10-b03, jgroups 2.5.0.GA.
> The code i use for making MulticastSockets is below. In combination with a default gateway and preferIPv4 this was the only way to make sure that my socket only received datagrams for the group it actually joined. Using the constructor with only a port results in a sokcet receiving ALL datagrams that are multicasted to that port (regardless of the group address it joined!).
> Can someone please give some feedback on this, and consider if this is a fix for UDP?
>         public static MulticastSocket createMulticastSocket(int TIMEOUT_MS, InetAddress group, int port) {
>                 MulticastSocket socket = null;
>                 try {
>                         socket = new MulticastSocket(new InetSocketAddress(group, port));
>                 } catch (BindException e1) {
>                         String warn = null == System.getProperty("java.net.preferIPv4Stack") ? "-Djava.net.preferIPv4Stack != true ??" : "java.net.preferIPv4Stack=true";
>                         log.warn("Unable to create the multicast socket at address " + group + ":" + port + "; I'll fall back to the windows solution (create the socket with port only) " + warn,e1);
>                         // Windows fallback
>                         try {
>                                 socket = new MulticastSocket(new InetSocketAddress(port));
>                         } catch (IOException e) {
>                                 throw new RuntimeException(e1);
>                         }
>                 } catch (Exception e1) {
>                         throw new RuntimeException(e1);
>                 }
>                 try {
>                         socket.setSoTimeout(TIMEOUT_MS);
>                         socket.joinGroup(group);
>                 } catch (Exception e1) {
>                         byte[] address = group.getAddress();
>                         String ad = address[0] + "." + address[1] + "." + address[2] + "." + address[3] + ":" + port + " " + e1.toString();
>                         try {
>                                 socket.close();
>                         } catch(Exception c){
>                                 log.warn("Ignore exception while closing bad multicast socket: " + c);
>                         }
>                         throw new RuntimeException(ad,e1);
>                 }
>                 return socket;
>         }

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