今天在做一个Vue小项目的时候，遇到了这样一个bug，终端输入npm run dev指令，本来按照我在package.json文件中配置的命令："dev": "webpack-dev-server --open --port 3000 --hot"，应该会运行webpack工具打包代码后，自动打开浏览器，监听3000端口，但是此时却在终端命令行提示出错，错误信息如下：

PS C:\Users\LXD\Desktop\my-vue\vue-cms> npm run dev

01.webpack-study@1.0.0 dev C:\Users\LXD\Desktop\my-vue\vue-cms

webpack-dev-server --open --port 3000 --hot

 

events.js:174

      throw er; // Unhandled 'error' event

      ^

Error: listen EADDRINUSE: address already in use 127.0.0.1:3000

    at Server.setupListenHandle [as listen2] (net.js:1253:19)

    at listenInCluster (net.js:1318:12)

    at GetAddrInfoReqWrap.doListen [as callback] (net.js:1451:7)

    at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:61:10)

Emitted 'error' event at:

    at emitErrorNT (net.js:1297:8)

    at process.tickCallback (internal/process/next_tick.js:63:19)

npm ERR! code ELIFECYCLE

npm ERR! errno 1

npm ERR! 01.webpack-study@1.0.0 dev: webpack-dev-server --open --port 3000 --hot

npm ERR! Exit status 1

npm ERR!

npm ERR! Failed at the 01.webpack-study@1.0.0 dev script.

npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:

npm ERR!     C:\Users\LXD\AppData\Roaming\npm-cache_logs\2019-05-23T14_10_58_853Z-debug.log

PS C:\Users\LXD\Desktop\my-vue\vue-cms>

根据错误提示，Error: listen EADDRINUSE: address already in use 127.0.0.1:3000，意思是3000端口已经被占用。这时，我寻找的解决方案为：

1. 打开cmd

2. 运行netstat -ano，找到报错信息提示的端口号那一行，记住最后那个数字

　　3.接下来运行tskill “最后那个数字”，所以这里我运行的是tskill 8408

最后打开VSCode，在终端再次输入npm run dev，运行成功，问题解决。