抓取网页爬虫，利用socket 的典型应用 Web 服务器和浏览器：浏览器获取用户输入的URL，向服务器发起请求，服务器分析接收到的URL，将对应的网页内容返回给浏览器，浏览器再经过解析和渲染，就将文字、图片、视频等元素呈现给用户。(Crawl the web crawler, using the typical applications of socket Web server and browser browser: get user input URL request to the server, the server receives the URL analysis, the web content corresponding to return to the browser, the browser after parsing and rendering, will render the text, pictures, video and other elements to the user.)