From 4.19 to 4.21 - incompatible_unique_net_id

[grujicbr]

@Crzyhomer

Sorry for the troubles everyone, I wrote that to avoid our QA causing late night, last minute fires when we are trying to ship games. As you probably know, any commandline addition of the form
-no will disable an online subsystem. We use at least 7 at any given time, so its possible for mistakes to be made.

Many use this for different reasons, but what happened all to often (and on a Friday night no less) would be the server would be fine but some client would have one of these set. Our servers would assert that the FUniqueNetId wasn’t serializing the right type to play our game. QA would freak out and bug it but it was always user error.

I added this explicit check because I figured externally most teams expect compatible unique ids. As it would seem it has been discovered, you are free to remove the check in AGameMode::Prelogin().

That being said, I’m curious, how do you get around the automatic calls to RegisterPlayer that would probably complain. Do you overload these functions? Do you not use the session interface to manage multiplayer sessions? Just want to understand the paths you are treading.

Most client/server relationships should be talking compatible OnlineSubsystems. For example, it makes little sense for a Steam client to join a non Steam server and not authenticate. A lot of that pipeline was written in the base engine implementation. APlayerState has one FUniqueNetId, which should be the one defined by DefaultPlatformSubsystem in your DefaultEngine.ini file.

Hi,

Thank you for giving us more information on why exactly these changes were made. What I’m trying to figure out is how we are expected to implement “cross-platform” client/server. You mention that you would expect if you are using a steam client, to also be using a steam server online subsystem. The type check changes make sense if that is the assumption, but if you want to use a steam client with your own online subsystem how exactly are we suppose to approach this?

From my understanding, you expect the developer to create their own online subsystem (let’s call it TestOnlineSubSystem) and create their own UniqueID (FUniqueNetIdTest, which derives from unique net id etc). When the user boots up the game on steam / xbox / ps4 / epic launcher let’s say, they will be using that specific subsystem (xbox, ps4 etc). Where are we suppose to handle the conversion from FUniqueNetIdSteam (this is replicated from client to server by the means of FUniqueNetIdRepl) to FUniqueNetIdTest (on the server) in order to be used for TestOnlineSubSystem so that the type checking will pass?

Currently in order to get around this, I implemented my own uniqueID and inside the PreLogin / InitNewPlayer functions I will create my own subsystems type and pass that through and it will work, but I dont really understand what official approach to your new implementation should be. It appears that many developers are having the same problems / questions regarding this.