How to emit message from client side [node.js + socket.io] - node.js

Question

I am trying to emit message from client side with socket.io ...
Here is my client code:
var socket = io.connect('http://localhost/');
socket.on('connect', function(data){
setStatus('connected');
socket.emit('subscribe', {channel:'update.comment'});
});
Server:
io.sockets.on('connection', function (socket) {
socket.emit('message', { text : 'Welcome!' });
socket.on('subscribe', function (data) {
socket.join(data.channel);
redisClient.subscribe(data.channel);
});
});
Also I get this error message in console:
GET
http://localhost/socket.io?EIO=3&transport=polling&t=1442169984269-1
404 (Not Found)
Full serever:
var app = require('express')();
var http = require('http').Server(app);
var redis = require('ioredis');
var io = require('socket.io')(http);
redisClient = redis.createClient();
//look for connection errors and log
redisClient.on("error", function (err) {
console.log("error event - " + redisClient.host + ":" + redisClient.port + " - " + err);
});
io.sockets.on('connection', function (socket) {
socket.emit('message', { text : 'Welcome!' });
//on subscription request joins specified room
//later messages are broadcasted on the rooms
socket.on('subscribe', function (data) {
socket.join(data.channel);
redisClient.subscribe(data.channel);
});
});
redisClient.on('ready', function(data) {
console.log('#redis ready');
});
redisClient.on("message", function(channel, message){
console.log(channel);
var resp = {'text': message, 'channel':channel};
io.sockets.in(channel).emit('message', resp);
});
http.listen(3000, function(){
console.log('Listening on Port 3000');
});

Answer 1

New Problem Recognized:
Your server is listening on port 3000, but you are attempting to connect on port 80. The error message http://localhost/socket.io?EIO=3&transport=polling&t=1442169984269-1 has no port number on it so that defaults to port 80.
That error message means that your server-side socket.io code is not initialized correctly and thus is not listening for the HTTP request that starts all webSocket connections so when the browser tries to connect on that URL to initiate a socket.io connection, there's nobody on the server-side listening so the web server returns a 404 error back to the browser.
If you are using Express, this is the minimal socket.io initialization to hook it into your server:
var express = require('express');
var app = express();
var server = app.listen(8081);
var io = require('socket.io').listen(server);
For a plain HTTP server, this is the minimal socket.io initialization:
var app = require('http').createServer(handler)
var io = require('socket.io')(app);
app.listen(80);
As always, if you show us the socket.io and web server initialization code you are using, we can help you better with your specific code issue.