In Azure Web PubSub, How to receive messages in backend microservice for processing

dheeraj awale 1

Requirement:

My clients are using simple WebSocket connection to send messages. I want to receive these messages inside my backend .NET 8 web api and process them further to send fine-tuned data to some distributed cache services.

From documentation, I only understood that I can use backend to only send the Access URL with token to clients, and Hubs are for dealing with events only (not messages).

I don't see how to receive messages in the backend service itself, but I guess I will need to use 'WebPubSubClient' in backend service itself to receive & process messages.

Doubt:

For receiving messages, how to set up a WebSocket connection from backend service?
If not, Is it right approach to use Client SDK to receive messages in web api service (probably using it in continuous running hosted service) ?

Bruce (SqlWork.com) 70,216 Reputation points

2025-01-10T18:53:50.1966667+00:00

in general a websocket connection is persistent connection rather than a typical http request/response. It is a 2 way stream with no formal packet definition. Part of designing a websocket app is defining the packet structures.

signal/r is a communication library and protocol built on websockets. It implements common HUBs for the server side and supports packet routing. unless your clients are already using signal/r this is not an option.

you can easily code to receive raw messages. You code would replace the echo method:

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/websockets?view=aspnetcore-9.0

your clients will need to tell you what the packets structure is and any required protocol packets.

as hosting a websocket application requires a persistent connections to multiple clients, and typically there are dedicated resources for each connection, which is active for the life of the connection. so a websocket app ties up more resources than a standard website (which typically have a 90 second connection time limit) thus require a different hosting requirement. But azure web apps support websockets by default now.

the Azure Web PubSub is an optimized hosting option for websocket applications. but it does not control how the app is developed or tools, but supplies a library to simplify websocket programming. it supports .net, node, python, java and azure functions (via hooks).
dheeraj awale 1 Reputation point

2025-01-13T04:18:33.19+00:00

the Azure Web PubSub is an optimized hosting option for websocket applications. but it does not control how the app is developed or tools, but supplies a library to simplify websocket programming. it supports .net, node, python, java and azure functions (via hooks).

In our case, clients already have a pure websocket library in their language. They don't want to rely on azure web pub library and just need to start websocket connection via their library (which is still a websocket library). So, what do you think about this?

Is it possible to not use this pubsub specific library and still use the service?

signal/r is a communication library and protocol built on websockets. It implements common HUBs for the server side and supports packet routing. unless your clients are already using signal/r this is not an option.

This is not an option for me, clients strictly don't want to use 'yet another' sdk/library for websockets.
Bruce (SqlWork.com) 70,216 Reputation points

2025-01-14T17:15:16.1933333+00:00

your question is not clear.

websocket is peer to peer. implementing common hubs or message broadcast is a framework on top websockets. signal/r and the Web PubSub implement a framework to support multiple broadcast.

are you trying to connect to an existing websocket applications or supply a new websocket application.

1 answer

Laxman Reddy Revuri 1,755 Reputation points Microsoft Vendor

2025-01-20T09:02:49.3133333+00:00

Hi @dheeraj awale
Yes, you can use Azure Web PubSub without the Microsoft SDK by connecting directly via WebSockets. Clients can use any WebSocket library to connect using a Client Access URL, which includes an access token for authentication.
The URL format is: wss://<service_name>.webpubsub.azure.com/client/hubs/<hub_name>?access_token=<token>.
Clients can then send and receive messages in real-time, with custom message handling based on the defined packet structure.
By not using the Azure SDK, you lose features like automatic reconnections and simplified group management, requiring manual handling. Clients must be aware of the message packet structure for proper communication. Additionally, you’ll need to manage scalability and connection handling on your own, as Azure Web PubSub won't handle it for you.

Please accept as "Yes" if the answer provided is useful , so that you can help others in the community looking for remediation for similar issues.
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Laxman Reddy Revuri 1,755 Reputation points Microsoft Vendor

2025-01-24T05:08:20.55+00:00

Hi @dheeraj awale
Following up to see if you have chance to check my previous response and help us with requested information to check and assist you further on this.

Laxman Reddy Revuri 1,755 Reputation points Microsoft Vendor

2025-01-27T03:32:47.8166667+00:00

Hi @dheeraj awale
Following up to see if you have chance to check my previous response and help us with requested information to check and assist you further on this.
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