Likely Unity's fault: "Only one usage of each socket address (protocol/network address/port) is normally permitted"

[megalithos]

Yes, I submitted the same issue before.

I don't know how to reproduce, I get the issue after some time when I have stopped and started play mode in unity editor multiple times. It gets fixed when I restart the unity editor.

[tom-weiland]

#53 was the previous issue (just for reference).

I had someone else complain about this same error on Discord just the other day. It's caused by the socket not being shut down correctly (even though—as far as I know—it should be when calling Server.Stop in OnApplicationQuit), and restarting the editor fixes it because that cleans it all up.

I myself haven't run into this error in several months, which makes debugging it virtually impossible. Any additional information about in which scenarios/what you were doing when the error occurs would be extremely helpful, particularly if you notice any patterns.

Even just putting a Debug.Log line after the Server.Stop call to confirm that it's running when you get the error would be a good start.

[megalithos]

I have a bit more info: my friend is making rpg with unity and he gets the same error with Mirror networking solution. He also fixes it just by restarting Unity.

[tom-weiland]

That's helpful to know, but still isn't definitive—either Mirror has the same problem or something about the Unity editor prevents it from shutting sockets down properly...

The last time I personally ran into this (months and months ago), I think it may have been after making code changes while the editor was in play mode. Perhaps when Unity rebuilds/reloads the code it either messes with running sockets or prevents the shutdown code from running? That was a long time ago and may have just been a one-off though, so if anyone else can provide more context regarding the conditions/timing/circumstances of this error, that'd be a big help.

[megalithos]

Yeah that sounds like a valid theory.
My guess is that the bug happens with some chance (like 0,1% chance) (lol) when the code is edited & unity is stopped while it is running like you said. So it would be internal bug in unity itself.

[tom-weiland]

when the code is edited & unity is stopped while it is running

Yeah, I've noticed it happening under those circumstances, but I can't confirm that that's the only time it happens :/