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no sACN over 127.0.0.1 (Loopback)
Posted: Mon Nov 27, 2017 2:51 pm
by sstaub
v5.2.2 I get no sACN output over the the loopback ip. The automatic selection of the Network Interface is off. Tested with Wireshark and sACNView, nothing
is send.
Posted: Mon Nov 27, 2017 3:46 pm
by admin
MacOS will only direct multicast packets to the loopback interface when there are no other interfaces available. This is true even when the socket is bound to the loopback address. If you shut off WiFi and Ethernet, MacOS will then direct multicast sACN to the loopback interface. This shouldn't be an issue, however, because receiving software running on the Mac that wants to listen to multicast shouldn't care if it is coming through the loopback interface or another active interface. The confusing thing might be if you are looking for the packets with Wireshark, you won't see them while capturing loopback. If you need to specifically use the loopback address (as opposed to the loopback interface which is a subtly different thing) then you can use LXConsole's DMX Out preferences to unicast to 127.0.0.1. If you are writing software that wants to listen to LXConsole's sACN output on the same computer through the loopback interface, don't bind your socket to 127.0.0.1 and just join the multicast group(s) and it should be fine.
Posted: Tue Nov 28, 2017 4:41 am
by admin
Actually, to get multicast sACN to work with only the loopback interface active, you may need to use the following in a terminal:
sudo route add -net 239.255.0.1 127.0.0.1
Packets appear in Wireshark without doing this (not sure why) However listening software cannot join the multicast group until added manually to loopback with the route command.
no sACN over 127.0.0.1 (Loopback)
Posted: Wed Nov 29, 2017 5:15 pm
by sstaub
Thank you for the responses, I forgot about multicast for sACN.
That makes the things for me clearer.
Posted: Wed Nov 29, 2017 6:30 pm
by admin
If you use route to direct 239.255.0.1 to 127.0.0.1, don't forget to put it back. Or, you might wonder why the lights aren't working when you go to use your computer in the theatre. (speaking from experience here...)
The route command does not seem to persist over a re-boot of the computer. However, you can also use
sudo route delete 239.255.0.1
to undo the effect of
sudo route add -net 239.255.0.1 127.0.0.1