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From Mitch Granger <mitch.gran...@sophos.com>
Subject Re: multicast 'timeToLive' doesn't seem to work
Date Thu, 24 Sep 2009 17:05:33 GMT


Bruce Snyder wrote:
> On Wed, Sep 23, 2009 at 5:57 PM, themitchy <mitch.granger@sophos.com> wrote:
>> This is how I'm setting timeToLive:
>>
>> <transportConnector name="openwire" uri="tcp://0.0.0.0:61616"
>> discoveryUri="multicast://default?timeToLive=20"/>
>>
>> When I check on the packets with Wireshark the TTL is still 1.
>>
>> That setting does seem to be doing _something_ since if I set it too high it
>> won't even start.
>>
>> Anyone ever used this successfully?  Maybe it just doesn't do what I think
>> it should (Like so many things in life)...
> 
> That particular timeToLive property applies to the java.net.MulticastSocket:
> 
> http://java.sun.com/j2se/1.5.0/docs/api/java/net/MulticastSocket.html#setTimeToLive(int)
> 
> A value of 1 for the timeToLive on a MulticastSocket means keep
> packets on the local network. Anything higher than that will cause
> packets to expand their range beyond the local network.
> 
> What is it that you're trying to do exactly?

We are trying to get packets beyond the local network.

Turns out java.net.MulticastSocket prefers ipv6 if it is installed.  So 
we added

  -Djava.net.preferIPv4Stack=true

To the java opts when starting AMQ and it worked just fine.

> 
> Bruce
> --
> perl -e 'print unpack("u30","D0G)U8V4\@4VYY9&5R\"F)R=6-E+G-N>61E<D\!G;6%I;\"YC;VT*"
> );'
> 
> ActiveMQ in Action: http://bit.ly/2je6cQ
> Blog: http://bruceblog.org/
> Twitter: http://twitter.com/brucesnyder

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