Java网络编程实例——简单模拟在线聊天

1、前提知识

需要知道简单的IO流操作，以及简单的UDP发送数据包的原理。

需要用到的类：DatagramSocket、DatagramPacket

UDP数据包基于DatagramSocket发送和接收，DatagramPacket用于封装数据包

看下案例：

客户端发送消息：

正常情况下从控制台读信息，封装到DatagramPacket之中，再由DatagramSocket的send方法发出

读取到bye的时候退出聊天

public class UdpOnlineClient {

    public static void main(String[] args) throws IOException {
        
        DatagramSocket socket = new DatagramSocket(10000);

        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));

        while (true) {

            String data = bufferedReader.readLine();
            byte[] datas = data.getBytes();

            DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress("localhost", 9999));

            socket.send(packet);

            if (data.equals("bye")){
                break;
            }

        }
        socket.close();
    }

}

服务端接收消息：

DatagramSocket的receive方法接收客户端发送的消息，打印到控制台，如果信息是bye则退出聊天

public class UdpOnlineServer {

    public static void main(String[] args) throws IOException {

        DatagramSocket socket = new DatagramSocket(9999);

        while (true){

            byte[] buffer = new byte[1024];

            DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);

            socket.receive(packet);
            String msg = new String(packet.getData(), 0, packet.getLength());

            System.out.println(msg);

            if(msg.equals("bye")){
                break;
            }
        }
        socket.close();

    }

}

试验：正常开启客户端和服务端后：

客户端发送消息：

服务端接收到信息即成功：

有了这个思路，我们只需要把发送和接收封装成发送类和接收类，使用多线程即可实现聊天了

2、实现思路：

创建UDP发送实现类TaskSend、UDP接收实现类TaskReceive，以及模拟多线程通信的通信类ChatThread1、ChatThread2

UDP发送实现类TaskSend：

public class TaskSend implements Runnable{
	
    private String sendIP;
    //自己的服务端口
    private int ownPort;
    private int sendPort;
    //读取控制台输入流
    private BufferedReader bufferedReader;
    private DatagramSocket socket;

    public TaskSend(String sendIP, int ownPort, int sendPort) {
        this.sendIP = sendIP;
        this.sendPort = sendPort;
        try {
            socket = new DatagramSocket(ownPort);
            bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        } catch (SocketException e) {
            e.printStackTrace();
        } finally {
        }
    }

    //发送消息
    public void run() {
        while (true) {

            try {
                String data = bufferedReader.readLine();
                //打印自己的消息
                System.out.println("我："+data);
                byte[] datas = data.getBytes();

                DatagramPacket packet = new DatagramPacket(datas, 0, datas.length,new InetSocketAddress(sendIP,sendPort));

                socket.send(packet);
                if (data.equals("bye")) {
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
            }
        }
        socket.close();
    }
}

UDP接收实现类TaskReceive：

public class TaskReceive implements Runnable{

    private int ownPort;
    //发送信息的人
    private String msgOwner;
    private DatagramSocket socket;

    public TaskReceive(int ownPort, String msgOwner) {
        this.msgOwner = msgOwner;
        try {
            socket = new DatagramSocket(ownPort);
        } catch (SocketException e) {
            e.printStackTrace();
        } finally {
        }
    }
	
    //接收消息
    public void run() {
        while (true) {
            try {
                byte[] buffer = new byte[1024];
                DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
                socket.receive(packet);
                String msg = new String(packet.getData(), 0, packet.getLength());
                System.out.println(msgOwner+"："+msg);

                if (msg.equals("bye")) {
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
            }
        }
        socket.close();
    }
}

之后使用两个通信类开启多线程模拟一下：

模拟老师

public class ChatThread1 {

    public static void main(String[] args) {
        new Thread(new TaskSend("localhost",9999,10000)).start();
        new Thread(new TaskReceive(9998,"老师")).start();
    }

}

模拟学生

public class ChatThread2 {

    public static void main(String[] args) {

        new Thread(new TaskReceive(9999,"学生")).start();
        new Thread(new TaskSend("localhost",9998,10001)).start();
    }

}

实例：

学生

老师

到此简单的在线聊天功能就完成了，可以巩固一下之前学习的网络知识

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