cloud9中的角度6-ERR_CONNECTION_TIMED_OUT

Question

我正在尝试在Cloud 9（免费版）中使用angular 6。当我点击时：

**ng serve --open**

一切似乎都正常，我明白了：

Angular Live Development Server is listening on localhost:4200, open your browser on http://localhost:4200/
Date: 2018-07-01T10:56:41.798Z
Hash: e8e3505bb172de5054c9
Time: 12051ms
chunk {main} main.js, main.js.map (main) 10.7 kB [initial] [rendered]
chunk {polyfills} polyfills.js, polyfills.js.map (polyfills) 227 kB [initial] [rendered]
chunk {runtime} runtime.js, runtime.js.map (runtime) 5.22 kB [entry] [rendered]
chunk {styles} styles.js, styles.js.map (styles) 15.6 kB [initial] [rendered]
chunk {vendor} vendor.js, vendor.js.map (vendor) 3.07 MB [initial] [rendered]
:information_source: ｢wdm｣: Compiled successfully.

但是当我进入-> localhost：4200 几秒钟后，我得到ERR_CONNECTION_TIMED_OUT 有谁知道可能是什么问题？谢谢。