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Question How to detect when a disconnection has happened?

Discussion in 'NetCode for ECS' started by EmmaPrats, Jan 17, 2023.

  1. EmmaPrats

    EmmaPrats

    Joined:
    Apr 19, 2019
    Posts:
    6
    1. Detecting disconnection from Client in the Server

    Is there a callback I can listen to?

    I know that when a client disconnects, its "NetworkConnection" entity (the one that has a 
    NetworkIdComponent
    ) is destroyed in the Server World. Clearly, Netcode for Entities does detect when a client disconnects. How can my server's logic detect that too?

    I am aware that there is a "proper" way to disconnect with NetworkStreamRequestDisconnect. I don't want to rely on that, if the client crashes or the player kills the game's process I want to know that they disconnected.

    2. Detecting disconnection from Server in the Client

    What is the appropriate way?

    Thank you for your help!
     
    EmmaPrats, Jan 17, 2023
    #1

  2. NikiWalker

    NikiWalker

    Unity Technologies

    Joined:
    May 18, 2021
    Posts:
    163
    Hey Emma,

    Yes, you can track both connections and disconnections via the optional `ConnectionState` `ICleanupComponentData`.

    "PlayerList" is a new sample showing this feature off, found here: https://github.com/Unity-Technologi...ster/NetcodeSamples/Assets/Samples/PlayerList
    This sample uses RPCs to create a "feed" of players who have connected/disconnected.
    One other approach (which isn't demonstrated here) is to implement this behaviour via a static-optimized ghost (with an IBufferElementData containing all connected players).

    For this implementation, take a look at the server logic here: https://github.com/Unity-Technologi.../Samples/PlayerList/ServerPlayerListSystem.cs

    ConnectionState is added on like 67, where we have a query of all new `NetworkStreamConnection` entities, where we add the optional component.

    New joiners are handled in the `HandleNewJoinersJob` on line 101. We wait for a client to send an RPC containing their `Username`. Thus, each client must opt-into being seen in the player list. Obviously, for your own game, you can source usernames however you like. E.g. The GameServer could communicate with a backend instead.

    For disconnecting players (regardless of disconnect reason): The `NotifyPlayersOfDisconnectsJob` job on line 184 will show you the query, and how it's used to detect disconnects.

    The `ClientPlayerListSystem`:
    • Registers a username with the "PlayerList" sub-system.
    • Receives these "PlayerList" change events.
    • Uses a cache of this data to draw the Player List, and all NOTIFICATIONS (via IMGUI).

    You can also use new controls in the "Multiplayer > Window: PlayMode Tools" to test various forms of disconnect. The next few pre-releases will contain improvements to this window.
     
    Last edited: Jan 17, 2023
    NikiWalker, Jan 17, 2023
    #2
    KindredKara, PolarTron and EmmaPrats like this.