What happens to the queued packets when socket is reconnected? Is there even a queue for packets?

[karagenc]

I'm asking for socket.io-client.

As you can see here and here, when a packet needs to be sent, the packet is encoded and sent directly with Engine.IO socket.

Is there a queue for packets in case packet never gets sent? What happens when a packet send fails?

[darrachequesne]

If the socket is not connected, the packet is buffered: https://github.com/socketio/socket.io-client/blob/b466c6f0b1dd5ef1a2149abc89d1884d376c0eee/lib/socket.ts#L190

If it is connected but fails to be sent at the Engine.IO level, it seems the packet is simply discarded/lost, as the writeBuffer here is not used when receiving a close event. Which is a bit surprising actually, we could maybe try to send it upon reconnection. What do you think?

[karagenc]

The send function of the browser WebSocket doesn't have a mechanism for error reporting. It could have given an exception or call a callback function on success. I think this is the only obstacle.

JavaScript sucks. For example you can check for an error with Go:
https://pkg.go.dev/github.com/gorilla/websocket#Conn.WriteMessage

But with the browser JavaScript WebSocket class, you can't.