4

I have a java application using multicast in order to advertise some entity - all worked fine when I tried the application a couple of weeks back. However, this is not the case anymore: I'm getting a

java.io.IOException: No route to host

exception when the unchanged application is started again. The application is sending DatagramPackets to 224.0.0.1.

My current system is Mac OS X Snow Leopard (10.6.7) with Java 1.6.0_24 installed.

I've tried out several approaches with the following outcomes: - search google -> some suggestions, none of which helped so far - disable firewall -> not successful - disable network interface (to force it to use the loopback) -> not successful - running it on Win machine -> successful, so I assume it definitely has something to do with the current (or changed/updated) system configuration

Any pointers or suggestions are greatly appreciated!

Cheers

Christof
  • 779
  • 8
  • 21
  • everything else on that machine can get to that address? ping/traceroute, etc? – John Gardner May 19 '11 at 15:54
  • that was my guess as well: what about icmp messages in general but that is perfectly fine. i maybe should point out that i'm testing it locally - so no real network in between as of now. – Christof May 19 '11 at 23:15
  • going to see whether wireshark helps me understand the matter a bit better. – Christof May 20 '11 at 00:16

1 Answers1

1

No route to host is caused by your process receiving an ICMP "host unreachable" message from some router on the path between you and the destination IP. Since you're getting this on a multicast address, I'd suspect something wrong with your router configuration.

Jim Garrison
  • 85,615
  • 20
  • 155
  • 190
  • 1
    it can also be caused right at the sending host by not finding the initial route, which points to the routing tables. – user207421 May 20 '11 at 04:00
  • but how come then that the application ran 3 weeks ago and now it doesn't anymore? If I add an entry in the host's routing table, what would be a suitable netmask to do so? Would 'route add 224.0.0.0 netmask 255.0.0.0 en1' be appropriate? – Christof May 20 '11 at 08:24