tutorial of node.js code sample fails with Error: listen EADDRINUSE

I am a beginner programmer that is trying to learn node.js using the following tutorial site http://www.nodebeginner.org/#hello-world

I got to the point where I was trying to set up the server but got an error with the below code

var http = require("http");

http.createServer(function(request, response) {
  response.writeHead(200, {"Content-Type": "text/plain"});
  response.write("Hello World");
  response.end();
}).listen(8888);

error:

events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: listen EADDRINUSE
    at errnoException (net.js:884:11)
    at Server._listen2 (net.js:1022:14)
    at listen (net.js:1044:10)
    at Server.listen (net.js:1110:5)
    at Object.<anonymous> (/Users/.........../server.js:7:4)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)

any help would be appreciated