Java网络编程之UDP实现原理解析

UDP实现通信非常简单,没有服务器,每个都是客户端,每个客户端都需要一个发送端口和一个接收端口。一个客户端向另一个客户端发送消息时,需要知道对方的IP和接收端口,所用到的类为DatagramSocket。

DatagramSocket socket =new DatagramSocket(),发送端socket,若不指定端口,系统自动分配

DatagramSocket socket =new DatagramSocket("接收信息端口"),接收端socket,需要指定接收端口

​ 若想客户端之间进行全双工通信,每个客户端都要有两个线程,一个用于发送信息,一个用于接收信息。

​ 那么UDP怎么实现私聊和群聊呢?(在本机一台电脑的情况下实现)

​ 首先私聊,客户端向另一个客户端发送消息,就要知道其IP(本机都是固定的localhost)和接收端口,也需要姓名进行标识,所以,每个客户端都至少要自己的姓名和接收端口,而且端口不可重复,否则会报端口被占用的错。

​ 其次群聊,由于在本机一台电脑上进行,接收端口各不相同,所以广播就不行了,此时就希望每个客户端在启动的时候,能够把自己的姓名和接收端口给存起来,然后就可以遍历进行群聊。

​ 实现:

  • 第一种,在每个客户端启动时,输入自己的姓名和接收端口,发送信息时,需要输入对方的接收端口号,如果输入时输入了多个端口,就是群发。那么这样每次发送信息时都要指定对方的端口。。。
  • 第二种,客户端启动时,输入姓名和接收端口,此时就把数据存起来,发送信息时,只用指定对方姓名即可。。。可用数据库存,可用文件存,我用的是XML来存。

要创建xml文件,路径在Operation类中

UdpClient.java:

public class UdpClient {

	public static void main(String[] args) {
		try {
			Scanner scanner = new Scanner(System.in);
			User user = new User();
			System.out.print("请输入用户名》》");
			String userName = scanner.next();
			if (Operation.userIsExist(userName)) {
				//如果此用户已经注册过,直接把注册时用的接收端口分配给他
				user = Operation.findUserByName(userName);
			}else {
				//未注册,用户自己指定端口
				while(true) {
					System.out.println("请输入接收端口》》");
					int port = Integer.parseInt(scanner.next());
					if (Operation.portIsExist(port)) {
						System.err.println("该端口已被使用,请重新输入。。。。");
						continue;
					}else {
						user.setName(userName);
						user.setPort(port);
						Operation.addUser(user);
						break;
					}
				}
			}
			new Thread(new SendMsg(user)).start();
			new Thread(new ReceiveMsg(user)).start();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

发送信息:

public class SendMsg implements Runnable{

	private User self = null;
	private DatagramSocket socket = null;
	private BufferedReader reader = null;
	public SendMsg(User self) {
		try {
			socket = new DatagramSocket();
			reader = new BufferedReader(new InputStreamReader(System.in));
			this.self = self;
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	@Override
	public void run() {	
		try {
			while(true) {
				String[] msg = reader.readLine().split("@");
				if (msg.length != 2) {
					System.err.println("注意格式:消息@对方名字(私聊)或all(群聊)");
					continue;
				}
				msg[0] = self.getName()+"说:"+msg[0];
				byte[] data = msg[0].getBytes();
				String toPerson = msg[1];
				if (("all").equals(toPerson)) {
					//群聊,获取所有用户,不管对方在不在线,都发过去
					List users = Operation.getUsers();
					for(User user:users) {
						if (self != user) {
							DatagramPacket packet = new DatagramPacket(data, 0,data.length,new InetSocketAddress("localhost",user.getPort()));
						    socket.send(packet);
						}
					}
				}else {
					//私聊
					try {
						DatagramPacket packet = new DatagramPacket(data, 0,data.length,new InetSocketAddress("localhost",Operation.findUserByName(toPerson).getPort()));
				        socket.send(packet);
					} catch (Exception e) {
						System.out.println("对方不在线。。。");
					}
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

接收消息:

public class ReceiveMsg implements Runnable{

	private DatagramSocket socket = null;
	public ReceiveMsg(User user) {
		try {
			socket = new DatagramSocket(user.getPort());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	@Override
	public void run() {
		try {
			while(true) {
				//准备接收包裹
				byte[] container = new byte[1024];
				DatagramPacket packet = new DatagramPacket(container,0,container.length);
				socket.receive(packet);
				byte[]data = packet.getData();
				String receiveData = new String(data, 0, data.length);
				System.out.println(receiveData);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		socket.close();
	}
}

操作XML文件类:

public class Operation {
	private static String FILE_PATH = "config/user.xml";     //文件目录
 
        //在xml文件中添加一个用户信息
	public static void addUser(User user)
	{
		InputStream in = null;
		SAXReader reader = new SAXReader();
		Document doc = null;
		try
		{
			in = new FileInputStream(FILE_PATH);
			doc = reader.read(in);
			Element root = doc.getRootElement();   //获取xml根节点,即users节点
			Element element = root.addElement("user");
			element.addElement("name").addText(user.getName());
			element.addElement("port").addText(String.valueOf(user.getPort()));
 
			FileOutputStream fos = new FileOutputStream(FILE_PATH);
			//格式化xml文件
			OutputFormat format = OutputFormat.createPrettyPrint();
			format.setEncoding("utf-8");
			XMLWriter writer = new XMLWriter(fos,format);
			writer.write(doc);
			writer.close();
		}
		catch (Exception e)
		{
			System.out.println("error");
		}
		finally
		{
			try
			{
			
				if(in != null)
					in.close();
			}
			catch (IOException e)
			{
				System.out.println("error");
			}
		}
	}
 
        //列出xml中所有用户信息
	public static List getUsers()
	{
		InputStream in = null;
		SAXReader reader = new SAXReader();
		Document doc = null;
		List users = new ArrayList<>();
		try
		{
			in = new FileInputStream(FILE_PATH);
			doc = reader.read(in);
			Element root = doc.getRootElement();
			List elements = root.elements();
			for (Element element : elements)
			{
				User user = new User();
				user.setName(element.elementText("name"));
				user.setPort(Integer.valueOf(element.elementText("port")));
				users.add(user);
			}
		}
		catch (Exception e1)
		{
			System.out.println("error");
		}
		finally
		{
			try
			{
				in.close();
			}
			catch (IOException e)
			{
				System.out.println("error");
			}
		}
 
		return users;
	}
	public static User findUserByName(String name) {
		InputStream in = null;
		SAXReader reader = new SAXReader();
		Document doc = null;
		try {
			in = new FileInputStream(FILE_PATH);
			doc = reader.read(in);
			Element root = doc.getRootElement();
			List elements = root.elements();
			for (Element element : elements)
			{
				if(name != null && name.equals(element.elementText("name"))) {
					User user = new User();
					user.setName(name);
					user.setPort(Integer.parseInt(element.elementText("port")));
					return user;
				}
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (DocumentException e) {
			e.printStackTrace();
		}
		return null;
	}
	
	public static boolean portIsExist(int port) {
		InputStream in = null;
		SAXReader reader = new SAXReader();
		Document doc = null;
		
		try {
			in = new FileInputStream(FILE_PATH);
			doc = reader.read(in);
			Element root = doc.getRootElement();
			List elements = root.elements();
			for (Element element : elements)
			{
				if(port == Integer.parseInt(element.elementText("port")))
					return true;
			}
			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (DocumentException e) {
			e.printStackTrace();
		}
		return false;
	}
        //判断某个用户是否存在该xml中
	public static boolean userIsExist(String name) 
	{
		InputStream in = null;
		SAXReader reader = new SAXReader();
		Document doc = null;
		try {
			in = new FileInputStream(FILE_PATH);
			doc = reader.read(in);
			Element root = doc.getRootElement();
			List elements = root.elements();
			for (Element element : elements)
			{
				if(name != null && name.equals(element.elementText("name")))
					return true;
			}
			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (DocumentException e) {
			e.printStackTrace();
		}
		return false;
	}
}

用户实体类:

public class User implements Serializable{

	private String name;//姓名
	private int port;//接收端口
	public String getName() {
		return name;
	}
	public int getPort() {
		return port;
	}
	public void setName(String name) {
		this.name = name;
	}
	public void setPort(int port) {
		this.port = port;
	}
	@Override
	public String toString() {
		return "User [name=" + name + ", port=" + port + "]";
	}
	
}

运行结果:

到此这篇关于Java网络编程之UDP实现原理解析的文章就介绍到这了,更多相关Java网络编程UDP内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家!

你可能感兴趣的