Java的Socket编程

Java中通过Socket实现客户端与服务器端的通信，大概步骤如下：

1）服务端创建ServerSocket，绑定服务器地址及端口并开始监听；
2）客户端建立socket连接，创建Socket对象，该Socket对象通过GetInputStream从主机读取信息，通过OutputStream向主机发送请求
3）服务端收到客户端的请求后，通过ServerSocket的accept方法创建Socket对象，该Socket对象通过GetInputStream读取客户端请求，通过OutputStream向客户端发送信息

 

下面是《JAVA 实例(Java Examples in a Nutsbell)》一书中的例子

服务器端：

package demo.socket;import java.io.BufferedReader;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.ServerSocket;import java.net.Socket;public class HttpMirror {public static void main(String[] args){try{int port = Integer.parseInt(args[0]);ServerSocket ss = new ServerSocket(port);while(true){Socket client = ss.accept();BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));PrintWriter out = new PrintWriter(client.getOutputStream());out.print("HTTP/1.0 200 /n");out.print("Content-Type: text/plain/n");out.print("/n");String line;while((line=in.readLine())!= null){if(line.length()==0) break;out.print(line + "/n");}out.close();in.close();client.close();}}catch(Exception e){e.printStackTrace();}}} 

 

客户端：

package demo.socket;import java.io.FileOutputStream;import java.io.InputStream;import java.io.OutputStream;import java.io.PrintWriter;import java.net.Socket;import java.net.URL;public class HttpClient {public static void main(String[] args){try{if((args.length != 1) && (args.length != 2)){throw new IllegalArgumentException("Wrong number of args.");}OutputStream outToFile;if(args.length==2){outToFile = new FileOutputStream(args[1]);}else{outToFile = System.out;}URL url = new URL(args[0]);String protocol = url.getProtocol();if(!protocol.equals("http")){throw new IllegalArgumentException("Must use 'http:' protocol.");}String host = url.getHost();int port = url.getPort();if(port == -1) {port = 80;}String filename = url.getFile();Socket socket = new Socket(host, port);InputStream fromServer = socket.getInputStream();PrintWriter toServer = new PrintWriter(socket.getOutputStream());toServer.print("GET " + filename + "/n/n");toServer.flush();byte[] buffer = new byte[4096];int bytes_read;while((bytes_read = fromServer.read(buffer)) != -1){outToFile.write(buffer, 0, bytes_read);}socket.close();outToFile.close();}catch(Exception e){e.printStackTrace();}}} 

 

运行：

java -cp [编译后class文件的路径，比如 D:/demo/output/classes] demo.socket.HttpMirror [端口号，比如9394]

 

在另外一个cmd命令行窗口运行

java -cp [编译后class文件的路径] demo.socket.HttpMirror [服务器路径，比如 http://localhost:9394/test.html]

 

则会显示：

 

HTTP/1.0 200

Content-Type: text/plain

 

GET /test.html

 

 

 

比如我机器上安装了apache服务器，打开http://localhost时会显示It works！的页面，运行下面命令时，

java -cp D:/demo/output/classes demo.socket.HttpClient http://localhost d:/works.html

则会得到该页面的信息，并写到D盘的works.html文件中

 

如果你的机器可以联网，你正在登陆新浪微博，也可以试下运行：

java -cp D:/demo/output/classes demo.socket.HttpClient http://t.sina.com.cn

 

则你会得到：

OK, Iamalive

 

 

 

当然，实际应用中可能还涉及到多线程、并发等方面的知识，这里就不多说了。（其实我也没怎么去了解，汗。。。）