Websockets and Chrome Dev Tools

Question

I have two queries about Websockets and how they are presented in Chrome Dev Tools. If that helps, I am using SockJS and StompJS on top of it. Spring framework on the backend.

What do those symbols "o", "a" and "h" represent?
After being disconnected from WebSocket, I got a message from the server (the last line in the picture attached). I did not expect that. What is it?

user_177819 · Answer

They are from SockJS communication protocol. You can see them in the SockJS client code here: https://github.com/sockjs/sockjs-client/blob/main/lib/main.js#L244

o: open connection
h: heartbeat
a: array of messages
m: single message
c: close connection

Websockets and Chrome Dev Tools

1 Answers