How do i know if connection is alive with websockets?

Question

I have a webapp, which is running in a browser. That webapp is connected to a server, which uses websockets. So the communication between the server and my client/browser is

Answer 1

A websocket connection object has a readyState field which will tell you if the connection is still active (from the dart documentation). The readyState can be either

0 - connection not yet established
1 - conncetion established
2 - in closing handshake
3 - connection closed or could not open

You can also define an event handler for the websocket close event if this is something you'd like to handle (try to reconnect, etc).

Answer 2

3 ways:

• rely on TCP to detect loss of connectivity, which will ultimately pop up in JS onclose event
• send WebSocket pings from server .. browsers will reply with WS pongs, loss of connectivity is probably more robustly detected also on client side
• send app level heartbeats from browser to server, server need to have logic to reply. you can't trigger WS pings from browsers (in JS)