A parser error causes the socket connection to reconnect but the old connection is not closed

[JoelBrenstrum]

If a parser error is encountered the socket connection is restarted but the old one is not closed

https://github.com/socketio/socket.io-client/blob/4f6030f2c4394bc51d63fe27ed3310d95b9e0a74/lib/manager.ts#L425

Socket.IO server version: 4.1.2

Server

import { Server } from "socket.io";

const io = new Server(3000, {});

io.on("connection", (socket) => {
  console.log(`connect ${socket.id}`);

  socket.on("disconnect", () => {
    console.log(`disconnect ${socket.id}`);
  });

  socket.on('notify', (msg: { channel: string; data: any }, callback) => {
    const { channel, data } = msg;
    socket.broadcast.emit(channel, data);
  });
});

Socket.IO client version: 4.7.2

Client

import { io } from "socket.io-client";

const socket = io("ws://localhost:3000/", {});

socket.on("connect", () => {
  console.log(`connect ${socket.id}`);
});

socket.on("disconnect", () => {
  console.log("disconnect");
});

//invalid emit, correct shape would be {channel: 'channel name': data: {records: []}}
socket.emit('notify', {records:[]})

We had an invalid emit in our code that resulted in us broadcasting (null, null) from the server. This was fine until a semi recent update to the socket.io-parser (socketio/socket.io-parser@3b78117). It causes the client to throw a parser error and to create a second connection to the hub, and slowly over time, this leaks a lot of connections.

I would expect that if the reconnection code is called on the client there is an attempt to safely close the old connection or to check that it is dead before attempting a reconnection. or to skip this behaviour for a parser error

Platform:

• Device: M1 MacBook pro
• OS: 14.1.1 (23B81)

[darrachequesne]

I was indeed able to reproduce the issue, thanks. I'm digging into this.

[darrachequesne]

For future readers:

This should be fixed by 04c8dd9, included in [email protected].