`npm start` not work as expected

[bruceauyeung]

os: centos 7 x64
electron version:

[root@host-10-114-51-177 electron-typescript-vue-starter-master]# electron -v
v5.0.6

chromium is installed:

[root@host-10-114-51-177 electron-typescript-vue-starter-master]# which chromium-browser
alias chromium-browser='chromium-browser --no-sandbox'
/usr/bin/chromium-browser

use npm to install node modules:

[root@host-10-114-51-177 electron-typescript-vue-starter-master]# npm install

electron@5.0.6 postinstall /root/electron-typescript-vue-starter-master/node_modules/electron
node install.js

npm WARN electron-exp@1.0.0 No repository field.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.9 (node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.9: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})

added 917 packages from 524 contributors in 57.074s

npm start runs without error but i expect an electron window is opened.

[root@host-10-114-51-177 electron-typescript-vue-starter-master]# npm start

electron-exp@1.0.0 start /root/electron-typescript-vue-starter-master
electron-forge start

✔ Checking your system
✔ Locating Application
✔ Preparing native dependencies
✔ Compiling Main Process Code
✔ Launch Dev Servers
✔ Compiling Preload Scripts
✔ Launching Application

Webpack Output Available: http://localhost:9000

i tried to open http://localhost:9000 using firefox but got error unable to connect