Use of nodnpmgenerator-material-app framework

  node.js, question

Install

$ npm install -g yo
$ npm install generator-material-app

$ mkdir app && cd $_
$ yo material-app
$ gulp build
$ npm start

npm starterror

julauddeMacBook-Pro:app julaud$ npm start
 
 > app@0.0.0 start /Users/www/npm/app
 > node bin/server.js
 
 events.js:141
 throw er;  // Unhandled 'error' event
 ^
 
 Error: listen EADDRINUSE 0.0.0.0:9001
 at Object.exports._errnoException (util.js:874:11)
 at exports._exceptionWithHostPort (util.js:897:20)
 at Server._listen2 (net.js:1234:14)
 at listen (net.js:1270:10)
 at net.js:1379:9
 at doNTCallback3 (node.js:450:9)
 at process._tickDomainCallback (node.js:397:17)
 at Function.Module.runMain (module.js:469:11)
 at startup (node.js:134:18)
 at node.js:961:3
 
 npm ERR!  Darwin 14.5.0
 npm ERR!  argv "/usr/local/bin/node" "/usr/local/bin/npm" "start"
 npm ERR!  node v4.2.1
 npm ERR!  npm  v2.14.7
 npm ERR!  code ELIFECYCLE
 npm ERR!  app@0.0.0 start: `node bin/server.js`
 npm ERR!  Exit status 1
 npm ERR!
 npm ERR!  Failed at the app@0.0.0 start script 'node bin/server.js'.
 npm ERR!  This is most likely a problem with the app package,
 npm ERR!  not with npm itself.
 npm ERR!  Tell the author that this fails on your system:
 npm ERR!  node bin/server.js
 npm ERR!  You can get their info via:
 npm ERR!  npm owner ls app
 npm ERR!  There is likely additional logging output above.
 
 npm ERR!  Please include the following file with any support request:
 npm ERR!  /Users/www/npm/app/npm-debug.log

I am very helpless, this suggests how to solve it, the operation department ~ \ (≡≡≡)/~!

Is there a big S to guide you?

Github address:https://github.com/michaelkrone/generator-material-app

Unknown Error Write an error handling process and it will not quit, but do not know what started