UE5.1 crashes every time I turn on my network

[BillBorez]

OK so UE5.1 won’t load at all when I have my network turned on, ( other versions of UE will load no problem ) it will load a project when the network is turned off , any project, even a blank I’ve created in UE5, but as soon as I turn on the network again it will instantly CTD.

This is the feedback screen I get:

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000000

UnrealEditor_UdpMessaging!UE::UdpMessaging::Private::DoJoinMulticastGroup() [D:\build++UE5\Sync\Engine\Plugins\Messaging\UdpMessaging\Source\UdpMessaging\Private\Transport\UdpMessageTransport.cpp:162]
UnrealEditor_UdpMessaging!UE::UdpMessaging::Private::JoinedToGroup() [D:\build++UE5\Sync\Engine\Plugins\Messaging\UdpMessaging\Source\UdpMessaging\Private\Transport\UdpMessageTransport.cpp:184]
UnrealEditor_UdpMessaging!FUdpMessageTransport::StartTransport() [D:\build++UE5\Sync\Engine\Plugins\Messaging\UdpMessaging\Source\UdpMessaging\Private\Transport\UdpMessageTransport.cpp:244]
UnrealEditor_UdpMessaging!<lambda_2a2de18caf381258aa803876dae009eb>::operator()() [D:\build++UE5\Sync\Engine\Plugins\Messaging\UdpMessaging\Source\UdpMessaging\Private\Transport\UdpMessageTransport.cpp:479]
UnrealEditor_Core!FTSTicker::Tick() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Containers\Ticker.cpp:110]
UnrealEditor!FEngineLoop::Tick() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:5605]
UnrealEditor!GuardedMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:202]
UnrealEditor!GuardedMainWrapper() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:107]
UnrealEditor!LaunchWindowsStartup() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:244]
UnrealEditor!WinMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:282]
UnrealEditor!__scrt_common_main_seh() [D:\a_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
kernel32
ntdll

I mean obviously UE is useless without a network, I can’t actually do anything.

Any ideas, tearing my hair out here.

[SupportiveEntity]

Hey there @BillBorez! This is a whacky one. So the UDP messaging plugin itself is causing this for some reason. It’s possibly running into issues at the driver level. So I’ve got a workaround and a possible fix.

The workaround is to disable the UDP messaging plugin. Which if you intend on using it will inherently not be useful as a workaround to you.

The possible solution is to try and update your network drivers. If that doesn’t work it may require a reinstallation of UE if the messaging plugin is the problem in this chain.

[BillBorez]

Thanks, I already tried a complete reinstall of 5.1. No joy.

I’ll try and disable the UDP messaging plugin and see what happens, but surely there has to be another cause for this if everyone else is running this plugin no problem.

I mean, all other versions of UE work apart from 5.1, it’s a complete mystery why this would be.

[SupportiveEntity]

I agree this is a very odd, hyper specific issue. Weird question, it crashes regardless of what networking type you use correct? This is a tough one since I’ve never seen anything like this with the base networking plugins.

[BillBorez]

Crashes both on ethernet and wifi.

I guess I could tether it to my phone network and see what happens though.

Weird.

[SupportiveEntity]

Since we can’t find a workaround and disabling the plugin doesn’t do it, we’re likely just going to have to report it as a bug in this case. You’re up to date on the windows network updates? It might be specific to your system configuration somehow unfortunately.

Report a Bug

[VioletLightwave]

I am experiencing exactly the same issue, turning off all network adaptors allows me to run UE 5.1 but as soon as I re-enable them then CTD. Super odd.

LoginId:ea19c0924ad0640b3607a9ad0053e5a6
EpicAccountId:c721db75f35d44c681ff8217ad5538c2

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000000

UnrealEditor_UdpMessaging
UnrealEditor_UdpMessaging
UnrealEditor_UdpMessaging
UnrealEditor_UdpMessaging
UnrealEditor_Core
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
kernel32
ntdll

[SupportiveEntity]

Hey there @VioletLightwave! Welcome to the community! Sorry to hear you’re experiencing one of the weirdest bugs I’ve ever seen! May I know your specs?

[SupportiveEntity]

Hey @BillBorez and @VioletLightwave, come across a couple workarounds the community had found for this issue if you’d like to give it a shot.

Unreal 5.1.0 Preview crashes on startup

Hello, After some research & test, here is my fix : 1/ In C:\Users\yourname\AppData\Local\UnrealEngine\5.1\Config Add : [/Script/UdpMessaging.UdpMessagingSettings] EnabledByDefault=False EnableTransport=True bAutoRepair=True MaxSendRate=1.000000 AutoRepairAttemptLimit=10 WorkQueueSize=1024 bStopServiceWhenAppDeactivates=True UnicastEndpoint=0.0.0.0:0 MulticastEndpoint=230.0.0.1:50000 MessageFormat=CborPlatformEndianness MulticastTimeToLive=1 EnableTunnel=False TunnelUnicastEndp…

Future Edit: Another possible fix, brought it here for anyone running across this thread in the future:

Frequent freezes/fps drop in Unreal Engine 5

For others that finds this thread hoping to solve stuttering in Unreal Engine Editor, go to your Project Settings → Plugins → UDP Messaging → EnableTransport (Set this to false). This solved it for me, I had the Editor FPS drop happen in 4.27, 5.0 and 5.1, no content browser up, empty scene and no blueprint windows up. PC specs: 3080Ti, 128GB ram, threadripper CPU (24cores) and so forth. PS: More info, UDP is related to network settings. If you are using a VPN that might cause this issue too…