June 25, 2022 1 min read

Azure Web PubSub: Native WebSocket at Scale

Azure Web PubSub provides native WebSocket support for building real-time applications at scale, with simpler client requirements than SignalR.

Service Creation

az webpubsub create \
    --resource-group myResourceGroup \
    --name myWebPubSub \
    --location eastus \
    --sku Standard_S1

Server-Side Messaging

using Azure.Messaging.WebPubSub;

var serviceClient = new WebPubSubServiceClient(connectionString, "notifications");

// Broadcast to all
await serviceClient.SendToAllAsync("System maintenance in 5 minutes");

// Send to user
await serviceClient.SendToUserAsync("user123", JsonSerializer.Serialize(new
{
    type = "notification",
    message = "You have a new message"
}));

// Send to group
await serviceClient.AddUserToGroupAsync("group1", "user123");
await serviceClient.SendToGroupAsync("group1", "Group update");

Event Handler

[Function("webpubsub")]
public async Task<WebPubSubEventResponse> Run(
    [WebPubSubTrigger("notifications", WebPubSubEventType.User, "message")]
    UserEventRequest request)
{
    // Process incoming message
    var message = request.DataType == WebPubSubDataType.Text
        ? request.Data.ToString()
        : Convert.ToBase64String(request.Data.ToArray());

    // Echo back
    return request.CreateResponse(
        $"Received: {message}",
        WebPubSubDataType.Text);
}

Client Connection

const ws = new WebSocket(clientAccessUrl);

ws.onopen = () => {
    console.log('Connected to Web PubSub');
    ws.send(JSON.stringify({
        type: 'joinGroup',
        group: 'notifications'
    }));
};

ws.onmessage = (event) => {
    const data = JSON.parse(event.data);
    console.log('Message:', data);
};

Summary

Azure Web PubSub offers native WebSocket support with powerful server-side messaging APIs, ideal for IoT, gaming, and collaboration apps.

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