Socket.io: Are "ping" and/or "pong" reserved events?

Created on 28 Jan 2016 · 4Comments · Source: socketio/socket.io

I have some basic code (see below) that works as expected when the events are named ding and dong but behaves very strangely when the events are named ping and pong

When the events are named ping and pong

The server code will log the "connect" and "disconnect" messages, but not the "ping" and "pong" messages
The client code will log the "ping" message and after a long wait (10+ seconds) will log the "pong" message, and if I keep waiting I'll get more "pong" message each 10+ seconds apart

Server Code

const fs             = require('fs');
const http           = require('http');
const path           = require('path');
const SocketIOServer = require('socket.io');

const app = new http.Server();
app.on('request', (req, res) => {

  const index = path.join(__dirname, 'public', 'index.html')

  fs.readFile(index, function (err, data) {
    if (err) {
      res.writeHead(500);
      return res.end('Error loading index.html');
    }

    res.writeHead(200);
    res.end(data);
  });
});
app.listen(3000, 'localhost');

const io = new SocketIOServer(app);


// could also use "connection"
io.on('connect', function (socket) {
  console.log(`${socket.id} "connect"`);

  socket.on('ping', (data) => {
    console.log('Receive "ping"');

    io.emit('pong', {});  
    console.log('Send "pong"');  
  });

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

Client Code

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <title>Socket.IO Events</title>
  </head>
  <body>
    <h1>Socket.IO Events</h1>

    <script src="/socket.io/socket.io.js"></script>
    <script>
      const socket = io();

      socket.on('pong', (data) => {
        console.log('Receive "pong"');
      });

      socket.emit('ping', {});
      console.log('Send "ping"');

    </script>
  </body>
</html>

I have no idea what is going on here. Also this may be related to #1951

Source

thebinarypenguin

👍3

Most helpful comment

Just trapped by the 'ping' event for few hours.
I think the official document may sync up with the document on GitHub?
Or maybe reserved event names can be noted on the document so that people won't be trapped again?

ajhsu on 7 Apr 2016

👍13

All 4 comments

I'm seeing strange behavior while using 'ping' / 'pong' event names - there does appear to be code in socket.io that does something with ping and pong, I don't have time to investigate further - changed name to 'drip' and 'drop'