We have been developing our Java applications under OSX for some time. Since switching to OSX Lion (version 10.7.1 now), we see sporadic issues around multicast packets going into the bit bucket and we don't know why. These are unit tests that are in the same VM connecting across the loopback. Sometimes disabling an interface resolves this. Other times it doesn't.
My only guess at this time is that it is related to multicast membership on different interfaces. I've noticed that even if an interface is offline (rj45 not plugged in or wifi disabled) that multicast groups still are attached to the interface. Is that proper?
IPv4 Multicast Group Memberships Group Link-layer Address Netif 188.8.131.52 <none> lo0 184.108.40.206 <none> lo0 220.127.116.11 <none> lo0 18.104.22.168 <none> lo0 22.214.171.124 1:0:5e:0:0:fb en1 << offline 126.96.36.199 1:0:5e:0:4b:4b en1 << offline 188.8.131.52 1:0:5e:0:0:1 en0 184.108.40.206 1:0:5e:0:0:fb en0 220.127.116.11 1:0:5e:0:4b:4b en0
Is there any way to tune these memberships? I've tried various commands with
route (del and others) and
ifconfig (up/down) to no avail. Am I barking down the wrong hole with this?
Turns out that if I unplug by hardwired ethernet and disable Wifi then my test can discover each other over multicast. But if either interface is enabled, it does not work.