proxy request *** from localhost:9999 to http://localhost:8080/ (ENOTFOUND)

[horrylala]

configuration

1.devServer configuration

devServer = {
  host: '0.0.0.0',
  port: 9999
}

2.proxyTable configuration

proxyTable: {
  '/ug-manage/': {
        target: 'http://localhost:8080/',
        changeOrigin: true
      },
}

Question

when i open browser, visit 'http://localhost:9999/ug-manage/getList ', the browser get 504 status code, and my terminal get :

[HPM] Error occurred while trying to proxy request /ug-manage/getList from localhost:9999 to http://localhost:8080/ (ENOTFOUND) (https://nodejs.org/api/errors.html#errors_common_system_errors)

Why it shows the error?

but when change the proxyTable:

proxyTable: {
  '/ug-manage/': {
        target: 'http://127.0.0.1:8080/',
        changeOrigin: true
      },
}

or

proxyTable: {
  '/ug-manage/': {
        target: 'http://0.0.0.0:8080/',
        changeOrigin: true
      },
}

it works.

so what exactly HMR did when translate localhost? it doesn't translate to '127.0.0.1'?