本例只做简单功能演示，代码并不严谨，只是说明客户端如何实现连接服务端简单代码。

代码在集成Eclipse工具下测试编译运行环境如下图所示：

客户端echoClient.java代码：

package com.zhengzz.echo; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.Socket; import java.net.UnknownHostException; class EchoC{ private Socket socket; public EchoC() { // TODO Auto-generated constructor stub try { socket = new Socket("localhost", 60000); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } public void Client() { try { BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream())); PrintWriter pw = new PrintWriter(socket.getOutputStream(), true); BufferedReader lbr = new BufferedReader(new InputStreamReader(System.in)); String linestr = null; while ((linestr = lbr.readLine()) != null) { pw.println(linestr); System.out.println(br.readLine()); if (linestr.equals("bye#")) { break; } } } catch (IOException e) { e.printStackTrace(); } } } public class echoClient { public static void main(String[] args) { new EchoC().Client(); } }

服务端echoServer.java代码：

package com.zhengzz.echo; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; class EchoS{ private ServerSocket serverSocket; public EchoS() { try { serverSocket = new ServerSocket(60000); } catch (IOException e) { e.printStackTrace(); } } public void Server() { while (true) { try { Socket socket = serverSocket.accept(); System.out.println("client:" + socket.getInetAddress() + ":" + socket.getLocalPort()); BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream())); PrintWriter pw = new PrintWriter(socket.getOutputStream(), true); String linestr; while ((linestr = br.readLine()) != null) { System.out.println(linestr); pw.println("--->" + linestr); } } catch (IOException e) { System.out.println("连接断开：（"); } } } } public class echoServer { public static void main(String[] args) { new EchoS().Server(); } }

我在Eclipse工具下直接调试结果如下：

下面我们再来看一个 HelloWord 级别的 Java Socket 通信的例子。通讯过程：

先启动 Server 端，进入一个死循环以便一直监听某端口是否有连接请求。然后运行 Client 端，客户端发出连接请求，服务端监听到这次请求后向客户端发回接受消息，连接建立，启动一个线程去处理这次请求，然后继续死循环监听其他请求。客户端输入字符串后按回车键，向服务器发送数据。服务器读取数据后回复客户端数据。这次请求处理完毕，启动的线程消亡。如果客户端接收到 "OK" 之外的返回数据，会再次发送连接请求并发送数据，服务器会为这次连接再次启动一个线程来进行响应。。。直到当客户端接收到的返回数据为 "OK" 时，客户端退出。

服务端源代码：

package com.defonds.socket.begin; import java.io.BufferedReader; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.InputStreamReader; import java.net.ServerSocket; import java.net.Socket; public class Server { public static final int PORT = 12345;//监听的端口号 public static void main(String[] args) { System.out.println("服务器启动...n"); Server server = new Server(); server.init(); } public void init() { try { ServerSocket serverSocket = new ServerSocket(PORT); while (true) { // 一旦有堵塞, 则表示服务器与客户端获得了连接 Socket client = serverSocket.accept(); // 处理这次连接 new HandlerThread(client); } } catch (Exception e) { System.out.println("服务器异常: " + e.getMessage()); } } private class HandlerThread implements Runnable { private Socket socket; public HandlerThread(Socket client) { socket = client; new Thread(this).start(); } public void run() { try { // 读取客户端数据 DataInputStream input = new DataInputStream(socket.getInputStream()); String clientInputStr = input.readUTF();//这里要注意和客户端输出流的写方法对应,否则会抛 EOFException // 处理客户端数据 System.out.println("客户端发过来的内容:" + clientInputStr); // 向客户端回复信息 DataOutputStream out = new DataOutputStream(socket.getOutputStream()); System.out.print("请输入:t"); // 发送键盘输入的一行 String s = new BufferedReader(new InputStreamReader(System.in)).readLine(); out.writeUTF(s); out.close(); input.close(); } catch (Exception e) { System.out.println("服务器 run 异常: " + e.getMessage()); } finally { if (socket != null) { try { socket.close(); } catch (Exception e) { socket = null; System.out.println("服务端 finally 异常:" + e.getMessage()); } } } } } }

客户端源代码：

package com.defonds.socket.begin; import java.io.BufferedReader; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.IOException; import java.io.InputStreamReader; import java.net.Socket; public class Client { public static final String IP_ADDR = "localhost";//服务器地址 public static final int PORT = 12345;//服务器端口号 public static void main(String[] args) { System.out.println("客户端启动..."); System.out.println("当接收到服务器端字符为 "OK" 的时候, 客户端将终止n"); while (true) { Socket socket = null; try { //创建一个流套接字并将其连接到指定主机上的指定端口号 socket = new Socket(IP_ADDR, PORT); //读取服务器端数据 DataInputStream input = new DataInputStream(socket.getInputStream()); //向服务器端发送数据 DataOutputStream out = new DataOutputStream(socket.getOutputStream()); System.out.print("请输入: t"); String str = new BufferedReader(new InputStreamReader(System.in)).readLine(); out.writeUTF(str); String ret = input.readUTF(); System.out.println("服务器端返回过来的是: " + ret); // 如接收到 "OK" 则断开连接 if ("OK".equals(ret)) { System.out.println("客户端将关闭连接"); Thread.sleep(500); break; } out.close(); input.close(); } catch (Exception e) { System.out.println("客户端异常:" + e.getMessage()); } finally { if (socket != null) { try { socket.close(); } catch (IOException e) { socket = null; System.out.println("客户端 finally 异常:" + e.getMessage()); } } } } } }

注意： Socket 输出流写数据方法是 writeUTF 时，输入流读取相关数据要用 readUTF。否则会抛 EOFException 异常。