Send2ue 2.4.3 "No instance of UnrealEditor found" on Linux/Debian 12

[Nanzikambe]

Creating a new bug here duplicating this one in the old repo

Steps to Reproduce the Problem:

• Addon: Send to Unreal
• Click Pipeline -> Exports -> Push Assets
• See error "No instance of UnrealEditor found" after a short delay with no additional info

• Error Log: None other than the error in "No instance of UnrealEditor found" in a popup
• OS: Debian GNU/Linux 12 (bookworm) x86_64
• Addon Version: Send to Unreal 2.4.3
• Blender Version: Blender 3.6.12
• Unreal Version: 5.4.2-33871570+++UE5+Release-5.4

Stuff already tried:

• 0.0.0.0 addresses were 127.0.0.1, I changed as per feedback in issue 695 this had no effect
• tried Blender 4.x, same result
• additionally tried send2ue versions: 2.4.3_v4fixes_28-03 and 2.4.5 with both Blender 3.6 and 4.x, same result

Work around:

Found a fix that's fairly self explanatory:

• Edit send2ue/dependencies/remote_execution.py and change 127.0.0.1 to 0.0.0.0 for the following constant declarations (at the top) DEFAULT_MULTICAST_BIND_ADDRESS and DEFAULT_COMMAND_ENDPOINT, as shown here:
• closed Blender
• deleted all .pyc files in send2ue sub directories
• started Blender and "Push Assets" works once more
  (note a restart is needed, using System > Reload scripts in Blender does not seem to reliably reload changed addons)

Observations:

• From reading descriptions of similar issues in Windows and Mac I think (but did not verify) loopback multicast behavior (127.0.0.1) differs on Linux as compared to Mac or Windows, using sudo ss -tunlp | egrep 6766 I could see UE upon first install was listening on 127.0.0.1,however using tcpdump -i lo port 6766I could only packets sent by send2ue, never a response until implementing the workaround above so both UE and Blender bind to 0.0.0.0, then I was able to see the packet response with tcpdump -- but not on loopback.
• Also related
• The following settings work but seem to interact with this problem somehow as well when set to 0 (in /etc/sysctl.conf)

net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.lo.rp_filter = 1
net.ipv4.conf.eth0.rp_filter = 1
net.ipv4.icmp_echo_ignore_broadcasts = 1

• Probably needs further investigating how these interact with the problem
• also note setting the kernel command-line ipv6.disable=1 or disabling ipv6 will cause UE to not start at all

[JoshQuake]

Thanks for the report! Hopefully we will be able to get this sorted. Losing out on linux and macos is no bueno