UDP接收发送图片

1、编写客户/服务器程序，客户端Client.java使用DatagramSocket对象将数据包发送到服务器，请求获取服务器端的图像，服务器端Server.java将图像文件包装成数据包，并使用DatagramSocket对象将该数据包发送到客户端。首先将服务器端的程序编译通过，并运行起来，等待客户的请求。

public class UDPServerExample implements Runnable {
	
	private DatagramSocket socket = null;
	private DatagramPacket receivePacket = null, sendPacket = null;
	
	
	public static void main(String args[]) {
		new UDPServerExample().start();
	}	
	public void start() {
		try {
			socket = new DatagramSocket(7000);				
			new Thread(this).start();//启动线程
		} catch (Exception e) {			
		}
	}
	public void run() {
		try {			
			while (true) {				
				byte[] buf = new byte[50];
				receivePacket = new DatagramPacket(buf, buf.length);
				socket.receive(receivePacket);
				if(receivePacket.getLength() > 0) { //接收到请求
					System.out.println("客户机的地址:" + receivePacket.getAddress().getHostAddress());
					System.out.println("正在等待");
					sendData(receivePacket.getAddress(),receivePacket.getPort());					
				}		
			}
		} catch (Exception e) {			
			e.printStackTrace();
		}
	}
	public void close() {
		
	}
	public void sendData(InetAddress address,int post) {
		FileInputStream fis = null;
		try {			
			byte[] buf = new byte[3072];	
			fis = new FileInputStream(new File("c://1.jpg"));	
			int read = 0;
			while((read=fis.read(buf)) != -1) {
				sendPacket = new DatagramPacket(buf, read,address,post);				
				socket.send(sendPacket);
				Thread.sleep(5);			
			}
			// 文件发送完毕，再发送一个数据报通知客户端
			if(read == -1) {				
				ByteArrayOutputStream out = new ByteArrayOutputStream();
				PrintStream pout = new PrintStream(out);
				pout.print("end");
				buf = out.toByteArray();
				sendPacket = new DatagramPacket(buf, buf.length, address, post);				
				socket.send(sendPacket);
			}			
			
		} catch (Exception e) {
			e.printStackTrace();				
		}finally{
			try {
				if(fis != null){
					fis.close();
				}
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}

2、客户端

public class UDPClientExample extends JFrame implements ActionListener,Runnable {
	
	private static final long serialVersionUID = 1L;
	private DatagramSocket socket = null;
	private DatagramPacket receivePacket = null, sendPacket = null;
	private JButton button = new JButton("获取图像");
	private JLabel label = new JLabel();
	private String serverIp = "127.0.0.1";
	private int serverPort = 7000;
	
	public UDPClientExample() {
		this.setTitle("I am a client");
		this.setSize(500, 500);
		this.setLocationRelativeTo(null);
		this.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
		button.addActionListener(this);
		this.add(button, "North");
		this.add(label, "Center");
		this.setVisible(true);
		
		try {
			// 创建一个DatagramSocket，使用随机端口
			socket = new DatagramSocket();
		} catch (SocketException e1) {			
			e1.printStackTrace();
		}		
	}
	
	public void start() {
		sendMessage(); //发送请求
		new Thread(this).start();//启动线程
		
	}
	public static void main(String args[]) {
		new UDPClientExample();
	}

	public void actionPerformed(ActionEvent e) {
			start();	
	}
	public void sendMessage() {
		try {			
			byte[] buf = new byte[]{'g','e','t'};
			sendPacket = new DatagramPacket(buf, buf.length, InetAddress
					.getByName(serverIp), serverPort);
			socket.send(sendPacket);
			buf = null;
			button.setEnabled(false);
		} catch (Exception e) {
			e.printStackTrace();				
		}
	}
	public void run() {
		receiveData();
	}
	public void receiveData() {
		try {	
			byte[] total = new byte[500*1024];			
			int start = 0;			
			byte buf[] = new byte[3072];
			while (true) {								
				receivePacket = new DatagramPacket(buf, buf.length);
				socket.receive(receivePacket);
				ByteArrayInputStream bin = new ByteArrayInputStream(
						receivePacket.getData());
				BufferedReader read = new BufferedReader(new InputStreamReader(
						bin));				
				String str = read.readLine();			
				if(str.startsWith("end")) {					
					break;
				}
				buf = receivePacket.getData();					
				// 将buf数组里的数据复制到total数组中
				System.arraycopy(buf, 0, total, start, receivePacket.getLength());
				start += receivePacket.getLength();					
			}
			ImageIcon icon = new ImageIcon(total);
			label.setIcon(icon);			
			//button.setEnabled(true);
			
		} catch (Exception e) {			
			e.printStackTrace();
		}
	
	}
}