UnrealLightmass stuck @ 0% Linux

When trying to build the lighting in UE4Editor, UnrealLightmass is spawned and runs but is put to sleep right away.
Here is all the relevant output from the terminal regarding UnrealLightmass


This error has to do with the firewalld settings or somehow UE4Editor using the wrong interface to communicate with UnrealLightmass.

I had to open up port 6666 so it could build the lighting.

Hi Salamanderrake,

Both the engine and Swarm must be set as exceptions when it comes to firewalls. Please make sure to list them as exceptions so that you do not receive any further warnings/blocks when utilizing build functionality.

Thanks for this, Salamanderrake. Opening up port 6666 UDP using firewalld took care of this problem for me on CentOS 7. Easy fix once you know the cause of the stall.

Works nicely on Fedora 26, thank you for the tip!