System design: WebSocket | Rush to learn websocket | Microsoft Azure

 Feb. 22, 2021

Here is the article. 

I like to read better about websocket. So I put together some keywords. 

1. Websocket
2. Keywords to look up later using Google:
3. native support
4. application gateway
5. all gateway sizes
6. websocket protocol - RFC6455
7. a full duplex communication 
8. a server and a client - TCP connection - a long running 
9. bidiectional - without polling as required in HTTP-based implementations 
10. low overhead 
11. unlike httP 
12. REUSE THE same TCP connection for multiple request/ responses 
13. more efficient utilization of resources 
14. HTTP post 90 and 443 - webSocket protocols 
15. backend server - the websocket enabled 
16. in apps - fast, real-time communication, such as chat, dashboard, and game apps 

Application Gateway provides native support for WebSocket across all gateway sizes. There is no user-configurable setting to selectively enable or disable WebSocket support.

WebSocket protocol standardized in RFC6455 enables a full duplex communication between a server and a client over a long running TCP connection. This feature allows for a more interactive communication between the web server and the client, which can be bidirectional without the need for polling as required in HTTP-based implementations. WebSocket has low overhead unlike HTTP and can reuse the same TCP connection for multiple request/responses resulting in a more efficient utilization of resources. WebSocket protocols are designed to work over traditional HTTP ports of 80 and 443.

You can continue using a standard HTTP listener on port 80 or 443 to receive WebSocket traffic. WebSocket traffic is then directed to the WebSocket enabled backend server using the appropriate backend pool as specified in application gateway rules. The backend server must respond to the application gateway probes, which are described in the health probe overview section. Application gateway health probes are HTTP/HTTPS only. Each backend server must respond to HTTP probes for application gateway to route WebSocket traffic to the server.

It's used in apps that benefit from fast, real-time communication, such as chat, dashboard, and game apps.