package.json

{
  "name": "socket.io.1.0",
  "version": "1.0.0",
  "description": "Socket.IO 1.0 using Primus",
  "main": "socket.io.1.0.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "repository": {
    "type": "git",
    "url": "https://gist.github.com/6113494.git"
  },
  "keywords": [
    "socket.io",
    "primus"
  ],
  "author": "Arnout Kazemier",
  "license": "MIT",
  "bugs": {
    "url": "https://gist.github.com/6113494"
  },
  "dependencies": {
    "primus-multiplex": "~0.1.2",
    "primus-emitter": "~0.1.0",
    "primus-rooms": "~0.1.6",
    "primus": "~1.1.2",
    "engine.io": "~0.6.3"
  }
}

socket.io.1.0.js

'use strict';

var Primus = require('primus')
  , http = require('http');

//
// Setup a server that Primus can listen on, pass it in the primus
// constructor, select `engine.io` as transformer, add plugins,
// ???, profit
//
var server = http.createServer();
var app = new Primus(server, { transformer: 'engine.io' });

app.use('multiplex', 'primus-multiplex')
   .use('emitter', 'primus-emitter')
   .use('rooms', 'primus-rooms');

server.listen(8080);

//
// Save the client in the root of directory or just use it directly
// <script src="http://localhost:8080/primus/primus.js"></script>
//

app.on('connection', function (socket) {
  socket.emit('hello', 'world');
  socket.join('room');
});

app.channel('foo').on('connection', function (socket) {
  socket.emit('hello', 'foo');
});

<script src="/primus/primus.js"></script>
<script>
var socket = Primus.connect('http://localhost:8080')

socket.on('hello', function (data) {
  console.log(arguments);
  socket.emit('foo', data);
});
</script>

socket.emit() doesn't work with Primus Emitter 2.x.

Must be used: socket.send()