Unregister and Reregister

In this tutorial, you'll learn how to:

• Reregister clients who are disconnected.
• Unregister clients who leave a channel so that resources are cleaned up.

Prerequisites

This tutorial requires the Hello World! app you have created earlier.

Reregister a Client

If a client is unable to register because of external factors, like a network connection failure, we determine whether the client has decided to leave and must be unregistered. If not, we reregister the client according to the reregister backoff period.

The reregister backoff is an incremental interval time between reregistrations. For example, if the reregister backoff time is 10 seconds, then the first time the application tries to reregister is after 10 seconds. The second reregister attempt happens after 20 seconds. The third reregister attempt happens after 30 seconds and so on until it reaches a set maximum backoff time. If you set the maximum backoff to 1 minute, then once 1 minute has elapsed, the backoff interval doesn't increase.

To reregister a client:

1. Set the reregister backoff and maximum backoff period in milliseconds.
2. Set unregistering to false.
3. Create an event on the client to handle the state changes. If the client isn't unregistering, register the client with a token into the channel again.

Update the joinAsync function in the HelloWorldLogic class to the following:

• CSharp
• Android
• iOS
• TypeScript

// Registering and reregistering a client 
private int _ReregisterBackoff = 200;
private const int _MaxRegisterBackoff = 60000;
private bool _Unregistering = false;

public async Task JoinAsync()
{
    Client = new Client(GatewayURL, ApplicationId);
    ChannelClaim[] channelClaims = new[] { new ChannelClaim(ChannelId) };
    string token = Token.GenerateClientRegisterToken(
        ApplicationId,
        Client.UserId,
        Client.DeviceId,
        Client.Id,
        null,
        channelClaims,
        SharedSecret
    );

    _Unregistering = false;
    Client.OnStateChange += async (client) =>
    {
        if (client.State == ClientState.Unregistered && !_Unregistering)
        {
            Log.Debug($"Registering with backoff = {_ReregisterBackoff}.");                   
            // Incrementally increase register backoff to prevent runaway process
            System.Threading.Thread.Sleep(_ReregisterBackoff);
            if (_ReregisterBackoff <= _MaxRegisterBackoff)
            {
                _ReregisterBackoff += _ReregisterBackoff;
            }
            DisplayMessage("Client unregistered unexpectedly, trying to re-register.");
            var reregisterChannels = await Client.Register(token).AsTask();
            _ReregisterBackoff = 200;    // Reset registering backoff
            OnClientRegistered(reregisterChannels);
        }
    };

    var channels = await Client.Register(token).AsTask();
    DisplayMessage("Client is registered!");
    OnClientRegistered(channels);
}

Unregister a Client

Unregistering clients when they leave is optional because the LiveSwitch Gateway automatically unregisters clients that are inactive for a period of time. However, unregistering clients cleans up resources immediately. To learn more about unregistering clients, refer to the Unregister section.

To unregister a client, invoke the unregister method of the client instance. In this code example, we set unregistering to true. This is only used for reregistering a client.

Paste the following code into the HelloWorldLogic class:

• CSharp
• Android
• iOS
• TypeScript

public void LeaveAsync()
{
    if (Client != null)
    {
        _Unregistering = true;
        Client.Unregister();
        Log.Info("Client has successfully unregistered.");
        DisplayMessage($"Client {Client.Id} has successfully unregistered from channel {Channel.Id}.");
    }
}

Uncomment UI Components

Go to the files that contain UI components and uncomment code to enable unregistering UI.

• CSharp
• Android
• iOS
• TypeScript

In MainWindow.xaml.cs, uncomment the code between the <Unregistered> and </Unregistered> tags.

Run Your App

1. Run your app in your project IDE.
2. Click Join.
3. Disable your device's Internet connection. In your project console, there is an error message describing a failure to connect because of a network issue.

   Note

   For TypeScript, the log is in the browser console.

4. Enable your device's Internet connection. In your project console, there is a message that the client has successfully joined.
5. Go to your LiveSwitch Console's homepage, and select the Hello World Application. There is only one client and one channel connected to your Hello World Application.
6. Go to your LiveSwitch Cloud's Dashboard page, and select the Hello World Application. There is only one client and one channel connected to your Hello World Application.
7. Click Leave.
8. Go to your LiveSwitch Console's homepage, and select the Hello World Application. There are no clients or channels connected to your Hello World Application.
9. Go to your LiveSwitch Cloud's Dashboard page, and select the Hello World Application. There are no clients or channels connected to your Hello World Application.

Congratulations, you've built your app to handle reregistering and unregistering.

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