KCP - created with cookie

[Ghetaldus]

Describe the bug
Spam with "created with cookie" with different cookie numbers is coming up when client gets timeout and then returns to the game.
For example when user minimize his app on the android and then returns after timeout have occured, his connection does not drop instantly but instead spam with cookies goes on for a while before disconnect happens.

[IMPORTANT] How can we reproduce the issue, step by step:
Please tell us how to reproduce your issue, STEP BY STEP, with one of our built in examples.

• Import latest Mirror version from git
• Open scene MirrorBasic from Basic example and enable debug for KCP
• Switch build target to Android and build it
• Start in Unity editor as server only
• Run your build as a client (I've used Bluestacks 5 emulator here)
• Minimize your app on the device and wait 10s for timeout and server to disconnect the client
• Now maximize back client's app and watch server's logs in Unity editor
• There will be plenty of lines with "[KCP] kcp2k.KcpServerConnection: created with cookie=1884780640" (see screenshot bellow)

Expected behavior
"created with cookie" should not be spammed so many times

Desktop (please complete the following information):

• OS: Windows 10
• Build target: Android
• Unity version: 2021.3.35 & 2022.3.21
• Mirror branch: 89.6.0

[Ghetaldus]

To add that I've just found out that this seems to happen only when using emulator to run your app.
Tested now with 2 real different devices and it did not reproduce with these.

[imerr]

Assuming these are packets from the previous connection still arriving at the server, we could check if the cookie is 0 before creating the connection @miwarnec?

Mirror/Assets/Mirror/Transports/KCP/kcp2k/highlevel/KcpServer.cs

Lines 311 to 347 in 9c9cc04

	if (!connections.TryGetValue(connectionId, out KcpServerConnection connection))
	{
	// create a new KcpConnection based on last received
	// EndPoint. can be overwritten for where-allocation.
	connection = CreateConnection(connectionId);
	// DO NOT add to connections yet. only if the first message
	// is actually the kcp handshake. otherwise it's either:
	// * random data from the internet
	// * or from a client connection that we just disconnected
	// but that hasn't realized it yet, still sending data
	// from last session that we should absolutely ignore.
	//
	//
	// TODO this allocates a new KcpConnection for each new
	// internet connection. not ideal, but C# UDP Receive
	// already allocated anyway.
	//
	// expecting a MAGIC byte[] would work, but sending the raw
	// UDP message without kcp's reliability will have low
	// probability of being received.
	//
	// for now, this is fine.
	// now input the message & process received ones
	// connected event was set up.
	// tick will process the first message and adds the
	// connection if it was the handshake.
	connection.RawInput(segment);
	connection.TickIncoming();
	// again, do not add to connections.
	// if the first message wasn't the kcp handshake then
	// connection will simply be garbage collected.
	}
	// existing connection: simply input the message into kcp