webpack-dev-server启动失败

webpack.config.js文件内容如下

module.exports = {
    devtool: 'eval-source-map', 
    entry: {
        app: [__dirname + '/app/index.js']
    }, 
    output: {
        path: __dirname + '/public/', 
        publicPath: "/public/", 
        filename: 'bundle.js' 
    },
    module: { //在配置文件里添加JSON loader
        loaders: [
            { test: /\.json$/, loader: "json" }, {
                test: /\.js$/,
                exclude: /node_modules/,
                loader: 'babel', 
                query: {
                    presets: ['es2015', 'react']
                }
            }, {
                test: /\.css$/,
                loader: 'style!css' 
            }, {
                test: /\.html$/,
                loader: 'html' 
            }


        ]
    },
    devServer: {
        contentBase: "/public", 
        historyApiFallback: true, 
        inline: true //实时刷新
    },
    // plugins: [
    //     new webpack.DefinePlugin({
    //         'process.env.NODE.ENV': "development"
    //     }),
    //     new webpack.HotModuleReplacementPlugin()
    // ]

}

---

sudo vi /etc/hosts
//添加
127.0.0.1 localhost