单工、半双工和全双工的定义

如果在通信过程的任意时刻，信息只能由一方A传到另一方B，则称为单工。

如果在任意时刻，信息既可由A传到B，又能由B传A，但只能由一个方向上的传输存在，称为半双工传输。

如果在任意时刻，线路上存在A到B和B到A的双向信号传输，则称为全双工。

用swing 做的简单界面 实现了客户端和服务器端全双工通信。

Server端代码： 

package cn.cblue.net1;

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

/**  
 * @Description: 服务端
 * @author huangzjb cblue2013@126.com
 * @Company Digital China
 * @date 2014-6-4 下午02:18:06
 * @version 1.0
 */

public class MyServer extends JFrame implements ActionListener {
	JTextArea jta = null;
	JTextField jtf = null;
	JButton jb = null;
	JPanel jp1 = null;
	JScrollPane jsp = null;
	PrintWriter pw = null;

	public static void main(String[] args) {
		new MyServer();
	}

	public MyServer() {
		jta = new JTextArea();

		jsp = new JScrollPane(jta);
		jtf = new JTextField(10);
		// 注册回车事件
		jtf.addKeyListener(new KeyListener() {

			@Override
			public void keyTyped(KeyEvent e) {
			}

			@Override
			public void keyReleased(KeyEvent e) {
			}

			@Override
			public void keyPressed(KeyEvent e) {
				if (e.getKeyCode() == KeyEvent.VK_ENTER) {
					sendMessage();
				}
			}
		});
		jb = new JButton("发送");
		jb.addActionListener(this);// 注册一个监听事件

		jp1 = new JPanel();
		jp1.add(jtf);
		jp1.add(jb);
		this.add(jsp, BorderLayout.CENTER);
		this.add(jp1, BorderLayout.SOUTH);
		this.setTitle("chat server");
		this.setSize(300, 200);
		this.setVisible(true);

		// 接收从客户端发送过来的消息
		try {
			ServerSocket ss = new ServerSocket(2222);
			Socket s = ss.accept();
			BufferedReader in = new BufferedReader(new InputStreamReader(s
					.getInputStream()));
			pw = new PrintWriter(s.getOutputStream(), true);// 写成pw = new PrintWriter(s.getOutputStream())会有问题
			while (true) {
				String info = in.readLine();
				String str = null;
				if (jta.getText() == null || "".equals(jta.getText())) {
					str = "Server:" + info;
				} else {
					str = jta.getText() + "\r\nServer:" + info;
				}
				jta.setText(str);
				jta.setCaretPosition(jta.getDocument().getLength());
			}

		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

	// 把信息给客户端
	@Override
	public void actionPerformed(ActionEvent e) {
		// TODO Auto-generated method stub
		if (e.getSource() == jb) {
			sendMessage();
		}
	}

	/**
	 * @Description: 发送消息给客户端
	 * @throws
	 */
	public void sendMessage() {
		String info = jtf.getText();
		pw.println(info);
		pw.flush();
		jtf.setText("");
		if (jta.getText() == null || "".equals(jta.getText())) {
			jta.append("Client:" + info);
		} else {
			jta.append("\r\nClient:" + info);
		}

		jta.setCaretPosition(jta.getDocument().getLength());// 设置滚动条自动滚动
	}
}

Client端代码：

package cn.cblue.net1;

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

/**  
 * @Description: 客户端
 * @author huangzjb cblue2013@126.com
 * @Company Digital China
 * @date 2014-6-4 下午02:18:24
 * @version 1.0
 */

public class MyClient extends JFrame implements ActionListener {

	JTextArea jta = null;
	JTextField jtf = null;
	JButton jb = null;
	JPanel jp1 = null;
	JScrollPane jsp = null;
	PrintWriter pw = null;

	public static void main(String[] args) {
		new MyClient();
	}

	public MyClient() {
		jta = new JTextArea();
		jsp = new JScrollPane(jta);
		jtf = new JTextField(10);
		// 注册回车事件
		jtf.addKeyListener(new KeyListener() {
			@Override
			public void keyTyped(KeyEvent e) {

			}

			@Override
			public void keyReleased(KeyEvent e) {

			}

			@Override
			public void keyPressed(KeyEvent e) {
				if (e.getKeyCode() == KeyEvent.VK_ENTER) {
					sendMessage();
				}
			}
		});

		jb = new JButton("发送");
		jb.addActionListener(this);// 注册一个监听事件

		jp1 = new JPanel();
		jp1.add(jtf);
		jp1.add(jb);
		this.add(jsp, BorderLayout.CENTER);
		this.add(jp1, BorderLayout.SOUTH);
		this.setTitle("chat client");
		this.setSize(300, 200);
		this.setVisible(true);

		// 接收从服务端发送过来的消息
		try {
			Socket s = new Socket("127.0.0.1", 2222);
			BufferedReader in = new BufferedReader(new InputStreamReader(s
					.getInputStream()));
			pw = new PrintWriter(s.getOutputStream(), true);
			while (true) {
				String info = in.readLine();
				String str = null;
				if (jta.getText() == null || "".equals(jta.getText())) {
					str = "Server:" + info;
				} else {
					str = jta.getText() + "\r\nServer:" + info;
				}
				jta.setText(str);
				jta.setCaretPosition(jta.getDocument().getLength());
			}

		} catch (IOException e) {
			e.printStackTrace();
		}

	}

	// 把信息给服务器端
	@Override
	public void actionPerformed(ActionEvent e) {
		if (e.getSource() == jb) {
			sendMessage();
			
		}
	}

	
	/**
	 * @Description: 发送消息给服务器端
	 * @throws
	 */
	public void sendMessage() {
			String info = jtf.getText();
			pw.println(info);
			pw.flush();
			jtf.setText("");
			if (jta.getText() == null || "".equals(jta.getText())) {
				jta.append("Client:" + info);
			} else {
				jta.append("\r\nClient:" + info);
			}
			jta.setCaretPosition(jta.getDocument().getLength());// 设置滚动条自动滚动
		}
	
}