gistfile1.js

var io          = require('socket.io-client');
var socket      = io.connect('http://my-server');

socket.on('status', function(status){
    if(status.exit == 1){
        lockScreen();
    }else if(status.sensei == 1){
        launchSite();
    }
});
socket.on('error', function(err){
    // Do something with the error
});

function lockScreen(){
    exec('/System/Library/CoreServices/Menu\\ Extras/User.menu/Contents/Resources/CGSession -suspend');
}

function launchSite(){
    exec('open -a Google\\ Chrome "http://github.com"');
}