说明：  java网络编程实例，分为客户端和服务器端，可以传送图片，记得把命名为a.jpg的图片放在当前目录，先运行服务器端程序，在运行客户端，点击get picture，例外还有两张JAVA初学的ppt，共五个文件
(java network programming instance, is divided into client and server side, you can send pictures, remember the name a.jpg picture on the current directory, first run the server-side program, run the client, click on get picture, there are two exceptions to Zhang JAVA beginner' s ppt, a total of five documents)