java - Netty 4 and 5 - multicast not working for me -

i have been trying udp multicast working netty 4.0.26 , 5.0.0.alpha2, without success. have adapted code this post in edited form supposedly works, not me. attached code echoes "send 1", "send 2" etc. corresponding packets never received.

in expression localsocketaddr = new inetsocketaddress(localaddr, mcast_port) have tried port 0 well, without success. kinds of other combinations of bind port , local address have been tried also.

the various socket options copied other post mentioned.

can tell me i'm doing wrong? java 8 on windows 8.1.

thanks much,

sean

import io.netty.bootstrap.bootstrap; import io.netty.buffer.bytebuf; import io.netty.buffer.unpooled; import io.netty.channel.channelfactory; import io.netty.channel.channelhandlercontext; import io.netty.channel.channeloption; import io.netty.channel.simplechannelinboundhandler; import io.netty.channel.nio.nioeventloopgroup; import io.netty.channel.socket.datagramchannel; import io.netty.channel.socket.datagrampacket; import io.netty.channel.socket.internetprotocolfamily; import io.netty.channel.socket.nio.niodatagramchannel;  import java.net.inetaddress; import java.net.inetsocketaddress; import java.net.networkinterface;  public class mcast {      private static final string local_addr = "192.168.0.18";     private static final string mcast_group = "239.254.42.96";     private static final int mcast_port = 9796;      public static void main(string[] args) throws exception {             thread sender = new thread(new sender());             thread receiver = new thread(new receiver());              receiver.start();             sender.start();              sender.join();             receiver.join();     }      private static class mcastsupport {             protected inetaddress localaddr;             protected inetaddress remoteaddr;             protected inetsocketaddress localsocketaddr;             protected inetsocketaddress remotesocketaddr;             protected datagramchannel chan;             protected bootstrap bootstrap;              public mcastsupport() {                     try {                             localaddr = inetaddress.getbyname(local_addr);                             remoteaddr = inetaddress.getbyname(mcast_group);                              localsocketaddr = new inetsocketaddress(localaddr, mcast_port);                             remotesocketaddr = new inetsocketaddress(remoteaddr, mcast_port);                              networkinterface nif = networkinterface.getbyinetaddress(localaddr);                              bootstrap = new bootstrap()                                     .group(new nioeventloopgroup())                                     .handler(new simplechannelinboundhandler<datagrampacket>() {                                             @override                                             protected void messagereceived(channelhandlercontext ctx, datagrampacket msg) throws exception {                                                     system.out.println("received: " + msg.content().getint(0));                                             }                                     })                                     .channelfactory(new channelfactory<niodatagramchannel>() {                                             @override                                             public niodatagramchannel newchannel() {                                                     return new niodatagramchannel(internetprotocolfamily.ipv4);                                             }                                     })                                     .handler(new simplechannelinboundhandler<datagrampacket>() {                                             @override                                             protected void messagereceived(channelhandlercontext ctx, datagrampacket msg) throws exception {                                                     system.out.println("received: " + msg.content().getint(0));                                             }                                     })                             .option(channeloption.so_broadcast, true)                             .option(channeloption.so_reuseaddr, true)                             .option(channeloption.ip_multicast_loop_disabled, false)                             .option(channeloption.so_rcvbuf, 2048)                             .option(channeloption.ip_multicast_ttl, 255)                             .option(channeloption.ip_multicast_if, nif);                      chan = (datagramchannel) bootstrap.bind(localsocketaddr).sync().channel();                      chan.joingroup(remotesocketaddr, nif).sync();                      } catch (throwable t) {                             system.err.println(t);                             t.printstacktrace(system.err);                     }             }     }      private static class sender extends mcastsupport implements runnable {             @override             public void run() {                     try {                             (int seq = 1; seq <= 5; ++ seq) {                                     bytebuf buf = unpooled.copyint(seq);                                     datagrampacket dgram = new datagrampacket(buf, remotesocketaddr, localsocketaddr);                                     chan.writeandflush(dgram);                                     system.out.println("send: " + seq);                                     thread.sleep(5000);                             }                      } catch (throwable t) {                             system.err.println(t);                             t.printstacktrace(system.err);                     }             }     }      private static class receiver extends mcastsupport implements runnable {             @override             public void run() {                     try {                             thread.sleep(5 * 5000);                     } catch (throwable t) {                             system.err.println(t);                             t.printstacktrace(system.err);                     }             }     } } 

the root of issue setting channeloption.ip_multicast_loop_disabled false. leaving out line (i.e. allowing ip_multicast_loop_disabled default true) allows multicast work expected. frankly, doesn't make lot of sense me, have no more time investigate.