node.js之启动监听

--该代码是nodejs启动时的一段。

--代码注释尚未补全，已有注释不当之处还望不吝赐教

/**
 * Module dependencies.
 */

var app = require('../app');
var debug = require('debug')('untitled:server');
var http = require('http');

/**
 * Get port from environment and store in Express.
 * 80端口看自己需要可修改
 */
var port = normalizePort(process.env.PORT || '80');
app.set('port', port);

/**
 * Create HTTP server.
 */

var server = http.createServer(app);

/**
 * Listen on provided port, on all network interfaces.
 *开启监听-可指定端口号和IP
 *这里注意若服务器hosts文件没有做127.0.0.1和localhost的映射那么可能需要下面的IP,否则你懂得
 *感谢@IPPP
 *至于公网映射推荐ngrok工具
 */
server.listen(port,'127.0.0.1');
console.log("服务已启动~~~");
//服务出错执行onError函数
server.on('error', onError);
//服务监听状态及其地址端口信息-尚未知晓如何使用！
server.on('listening', onListening);

/**
 * Normalize a port into a number, string, or false.
 */

function normalizePort(val) {
  var port = parseInt(val, 10);

  if (isNaN(port)) {
    // named pipe
    return val;
  }

  if (port >= 0) {
    // port number
    return port;
  }

  return false;
}

/**
 * Event listener for HTTP server "error" event.
 */

function onError(error) {
  if (error.syscall !== 'listen') {
    throw error;
  }

  var bind = typeof port === 'string'
    ? 'Pipe ' + port
    : 'Port ' + port;

  // handle specific listen errors with friendly messages
  switch (error.code) {
    case 'EACCES':
      console.error(bind + ' requires elevated privileges');
      //进程终止
      process.exit(1);
      break;
    case 'EADDRINUSE':
      console.error(bind + ' is already in use');
      process.exit(1);
      break;
    default:
      throw error;
  }
}

/**
 * Event listener for HTTP server "listening" event.
 */
function onListening() {
  var addr = server.address();
  var bind = typeof addr === 'string'
    ? 'pipe ' + addr
    : 'port ' + addr.port;
  debug('Listening on ' + bind);
  console.log('Listening on ' + bind);
}

 ---------------------------------------------------------------------------------------------------------------------

*、@IPPP

解决IP问题的灵感来源于
https://my.oschina.net/tearlight/blog/195543
很棒
曾经出现的问题是：不提供hostname只能使用localhost访问，后来不提供也能通过三种方式访问，很奇怪的说！