4.8.0 p3: default pawns don't spawn on clients after seamless ServerTravel

Development Programming & Scripting Multiplayer & Networking
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1

Is this a bug?

If it’s not a bug, how in world do i make them spawn? StartMatch also doesn’t spawn default pawns.

P.S.: if i need to spawn manually after a servertravel, what event do i need to put command in, OnPostSeamlessTravel or something (which isn’t exposed to blueprints though)?

2

UPDATE:

After some debugging i found out that clients don’t seem have a connection with server anymore after successfully changing level with ServerTravel, EVEN WITH “Use Seamless Travel” checked on GameMode.

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UPDATE 2:

Below is log from exact moment of executing ServerTravel:

log file

4

OK, it’s a confirmed BUG with multiplayer simulation in single process PIE.

Temporary workaround (as suggested on other threads) is to disable “Use Single Process” under PLAY > advanced options > multiplayer and also change “Editor Multiplayer Mode” to “Play As Client”.

Any ETA on this bugfix?

5

Hi ,

I haven’t seen this bug in particular before except with ShooterGame sample. Are you seeing this in your own project? Does it only occur during PIE, or in packaged games as well? Can you reproduce it in a new project? If so, it might be helpful if you could upload a small test project that reproduces this behavior and get us a download link so we can take a look. Thanks!

Additionally, you mention this is a confirmed bug. If you’ve seen this mentioned elsewhere with a bug report number, can you link that as well? I wasn’t able to find one internally when I looked for it.

6

Hi ,

Thanks for replying!

To answer your questions:

  1. As far as i know it’s only during PIE (and ONLY with a single process). I haven’t confirmed myself that it works in packaged games, but it does work in multiple processes in PIE like i mentioned.
  2. Example project to see it for yourself. Extract first, don’t run directly. If you have any trouble running it let me know.
  3. bug report numbers i could find are: UE-11271, UE-11391, UE-13111 and UE-3187. Funny enough you mentioned them all in this post
7

Those are all crash bugs involving Seamless Travel, and don’t specifically involve Clients not joining Server during ServerTravel.

PIE itself isn’t able to emulate networking correctly, so I tested this in a packaged game (adding some simple create, find, and join session functionality in Blueprints), and in that case it worked fine. For testing in editor, I think your solution of running with Use Single Process disabled should be fine.

Hope that helps!

8

Are there plans to make it work in PIE single process in future? current functionality is not user friendly for people that are new to Unreal Engine (networking). I mean i am somewhat experienced with engine and it took me a few days to figure out problem so i think it really should be looked at in future (if it’s technically possible).

Anyway, thanks for your effort !

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I have let networking team know, and they may have me enter a report for it (if there isn’t one already). I will update this post if I do.

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any news of seemless travel In PIE?

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If you override “CanServerTravel” to true when it checks for “in pie” to true, it works in non-multiplayer aspects. Its nice for easy testing of single player related functions. (its in gamemodebase)