It doesn't work if I modify the port in development mode of example6 part1

[AChao]

In development mode of example6 part1 , there is some code about port configuration.

// webpack.config.dev.js
 entry: [
        'webpack-dev-server/client?http://localhost:8082',
        'webpack/hot/dev-server',
        './src/index'
    ],

However, it doesn't work if I modify the port, for example, 8082, while the old port still works.