Following this guide produces an error

When I go through the following steps:
$ npm install
$ bower install
$ tsd install -r -o --save
$ gulp serve-dev

The final step results in the following error:
gulp-patterns] Watching files...
About to crank up node
PORT=7203
NODE_ENV=dev
*\* DEV **
events.js:85
throw er; // Unhandled 'error' event
^
Error: listen EADDRINUSE
at exports._errnoException (util.js:746:11)
at Server._listen2 (net.js:1129:14)
at listen (net.js:1155:10)
at Server.listen (net.js:1240:5)
at EventEmitter.listen (/##########/gulpTest/node_modules/express/lib/application.js:617:24)
at Object. (/##########/gulpTest/src/server/app.js:63:5)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
[10:15:38] **\* nodemon crashed: script crashed for some reason
[10:15:38] [nodemon] app crashed - waiting for file changes before starting...

NOTE: I replaced the path that was displayed in the output with ##########.