var http = require('http');
 var url = require('url');
 var path = require('path');
 var fs = require('fs');

 var dir, arg = process.argv[2] || ''; // 命令行第三个参数，用来接收目录，可为空，相对当前server.js文件的目录名称
 // 比如使用命令 node server debug，意思就是debug文件夹与server.js文件同级
 // 且你想以debug文件夹启动web服务

 http.createServer(function (req, res) {
 var pathname = __dirname + url.parse(req.url).pathname;
 dir = dir ? dir : pathname; // 记住dir(目录)
 pathname = dir ? pathname.replace(dir, dir + arg + '/') : pathname; // 替换文件静态路径
 if (path.extname(pathname) == "") {
 pathname += "/";
 }
 if (pathname.charAt(pathname.length - 1) == "/") {
 pathname += "index.html"; // 入口文件，此处默认index.html
 }

 fs.exists(pathname, function (exists) {
 if (exists) {
 switch (path.extname(pathname)) {
 case ".html":
 res.writeHead(200, {"Content-Type": "text/html"});
 break;
 case ".js":
 res.writeHead(200, {"Content-Type": "text/javascript"});
 break;
 case ".css":
 res.writeHead(200, {"Content-Type": "text/css"});
 break;
 case ".gif":
 res.writeHead(200, {"Content-Type": "image/gif"});
 break;
 case ".jpg":
 res.writeHead(200, {"Content-Type": "image/jpeg"});
 break;
 case ".png":
 res.writeHead(200, {"Content-Type": "image/png"});
 break;
 default:
 res.writeHead(200, {"Content-Type": "application/octet-stream"});
 }

 // res可以自己添加信息来简单交互 比如可以修改点header信息 或者修改返回的资源数据
 fs.readFile(pathname, function (err, data) {
 res.end(data);
 });
 }
 else {
 res.writeHead(404, {"Content-Type": "text/html"});
 res.end("<h1>404 Not Found</h1>");
 }
 });
 }).listen(8085, "127.0.0.5"); // 服务器端口

 console.log("server running at http://127.0.0.5:8085/");