socket.io switch between localhost & server - socket.io

Question

I am running socket.io on node.js on a local Mac machine.
I have setup port forwarding
I am using the following code:
socket = io.connect('XXX.XXX.137.143:1337');
socket.on('connect_failed', function(){
$.jGrowl('Connection Failed');
});
socket.on('disconnect', function(){
$.jGrowl('disconnected');
});
socket.on('connect', function () {
$.jGrowl('We are connected ' );
});
The IP address is my router IP address. This all works as expected.
However if I run the app on the same network as the router it fails to connect. It needs :
socket = io.connect('localhost'); // or the ip of the machine.
How do I determine I am on the same network as the machine and switch the IP setting ?
I tried:
if (location.hostname === "localhost" || location.hostname === "192.168.1.1")
{$.jGrowl("It's a local client!");
var IPaddress = 'http://192.168.1.6:1337';}
else {var IPaddress = '92.12.137.143:1337';
$.jGrowl("It's a remote client!")
}
This works locally but fails on another network that has IP = 192.168.1.1.
Cheers
Steve Warby

Answer 1

You could first attempt a connection to the public IP address and, if that fails, then attempt to connect locally. Here's one way to do that:
let socket = io.connect('http://92.12.137.143:1337');
socket.on('connect_error', handleNoConnect);
socket.on('connect_timeout', handleNoConnect);
socket.on('connect', onConnect);
function handleNoConnect() {
console.log("No connection to http://92.12.137.143:1337");
socket = io.connect('http://192.168.1.6:1337');
socket.on('connect_error', handleNoConnect2);
socket.on('connect_timeout', handleNoConnect2);
socket.on('connect', onConnect);
}
function handleNoConnect2() {
console.log("No connection to http://192.168.1.6:1337");
// decide what to do when you can't connect to either
}
function onConnect() {
console.log("connected");
// set other event handlers on a connected socket
socket.on('disconnect', function() {
console.log("disconnected");
});
}
Or, here's a more general purpose implementation that lets you pass in an array of URLs to try connecting to and it returns a promise that will resolve with the socket that made the connection or reject with an appropriate error.
function connect(list) {
let index = 0;
return new Promise((resolve, reject) => {
function next() {
if (index < list.length) {
let url = list[index++];
let doneThis = false;
let socket = io.connect(url);
socket.on('connect_error', handleNoConnect);
socket.on('connect_timeout', handleNoConnect);
socket.on('connect', () => {
// set property on socket object that tells you
// which URL it connected to
socket._url = url;
resolve(socket);
});
function handleNoConnect() {
if (!doneThis) {
doneThis = true;
console.log("No connection to " + url);
// try next item in the list
next();
}
}
} else {
reject(new Error("No connections succeeded"));
}
}
if (!list || !list.length) {
reject(new Error("Must pass array of URLs to connect()"));
return;
}
next();
});
}
connect(['http://92.12.137.143:1337', 'http://192.168.1.6:1337']).then(socket => {
// connected here
console.log("connected to " + socket._url);
// configure event handlers on the connected socket object here
socket.on('xxx', ...);
}).catch(err => {
// all connections failed here
console.log(err);
})