教你怎么用java實(shí)現客戶(hù)端與服務(wù)器一問(wèn)一答

運行效果

開(kāi)啟多個(gè)客戶(hù)端

服務(wù)端效果：

客戶(hù)端效果：

當一個(gè)客戶(hù)端斷開(kāi)連接：

代碼

因為代碼中有注釋?zhuān)揖椭苯淤N上來(lái)了

服務(wù)端：

package com.dayrain.server;
 
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;
 
public class NioServer {
    /**端口**/
    private static final int PORT = 8081;
    /**buffer大小**/
    private static final int DEFAULT_BUFFER_SIZE = 1024;
    private final Selector selector;
    private final ByteBuffer readBuffer = ByteBuffer.allocate(NioServer.DEFAULT_BUFFER_SIZE);
    private final ByteBuffer writeBuffer = ByteBuffer.allocate(NioServer.DEFAULT_BUFFER_SIZE);
 
    private static int count = 0;
 
    public static void main(String[] args) throws IOException {
        new NioServer().start();
    }
 
    public NioServer() throws IOException {
        //創(chuàng  )建一個(gè)服務(wù)端channel
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
 
        //設置為非阻塞
        serverSocketChannel.configureBlocking(false);
 
        //獲取服務(wù)器socket
        ServerSocket socket = serverSocketChannel.socket();
        //綁定ip和端口
        socket.bind(new InetSocketAddress(NioServer.PORT));
 
        //創(chuàng  )建多路復用選擇器，并保持打開(kāi)狀態(tài)，直到close
        selector = Selector.open();
 
        //將服務(wù)器管道注冊到selector上，并監聽(tīng)accept事件
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("server start on port: " + NioServer.PORT);
        start();
    }
 
    public void start() throws IOException {
 
        //selector是阻塞的，直到至少有一個(gè)客戶(hù)端連接。
        while (selector.select() > 0) {
            //SelectionKey是channel想Selector注冊的令牌，可以通過(guò)chancel取消（不是立刻取消，會(huì )放進(jìn)一個(gè)cancel list里面，下一次select時(shí)才會(huì )把它徹底刪除）
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            while (iterator.hasNext()) {
                SelectionKey selectionKey = iterator.next();
                iterator.remove();
                //當這個(gè)key的channel已經(jīng)準備好接收套接字連接
                if(selectionKey.isAcceptable()) {
                    connectHandle(selectionKey);
                }
 
                //當這個(gè)key的channel已經(jīng)準備好讀取數據時(shí)
                if(selectionKey.isReadable()) {
                    readHandle(selectionKey);
                }
            }
        }
    }
 
    /**
     * 處理連接
     * @param selectionKey
     */
    private void connectHandle(SelectionKey selectionKey) throws IOException {
        //注意，服務(wù)端用的是ServerSocketChannel，BIO中是ServerSocket
        ServerSocketChannel serverSocketChannel = (ServerSocketChannel) selectionKey.channel();
        SocketChannel socketChannel = serverSocketChannel.accept();
        if(socketChannel == null) {
            return;
        }
        socketChannel.configureBlocking(false);
        socketChannel.register(selector, SelectionKey.OP_READ|SelectionKey.OP_WRITE);
 
        System.out.println("客戶(hù)端連接成功，當前總數：" + (++count));
 
        writeBuffer.clear();
        writeBuffer.put("連接成功".getBytes(StandardCharsets.UTF_8));
        writeBuffer.flip();
        socketChannel.write(writeBuffer);
    }
 
    /**
     * 讀取數據
     * @param selectionKey
     */
    private void readHandle(SelectionKey selectionKey){
        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
        try {
            readBuffer.clear();
            int read = socketChannel.read(readBuffer);
            if(read > 0) {
                readBuffer.flip();
                String receiveData = StandardCharsets.UTF_8.decode(readBuffer).toString();
 
                System.out.println("收到客戶(hù)端消息: " + receiveData);
 
                writeBuffer.clear();
                writeBuffer.put(receiveData.getBytes(StandardCharsets.UTF_8));
                writeBuffer.flip();
                socketChannel.write(writeBuffer);
            }
 
        }catch (Exception e) {
            try {
                socketChannel.close();
            } catch (IOException ioException) {
                ioException.printStackTrace();
            }
            System.out.println("客戶(hù)端斷開(kāi)了連接~~");
            count--;
        }
    }
}

客戶(hù)端

package com.dayrain.client;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;
 
public class NioClient {
 
    private static final int PORT = 8081;
    private static final int DEFAULT_BUFFER_SIZE = 1024;
    private final Selector selector;
    private final ByteBuffer readBuffer = ByteBuffer.allocate(NioClient.DEFAULT_BUFFER_SIZE);
    private final ByteBuffer writeBuffer = ByteBuffer.allocate(NioClient.DEFAULT_BUFFER_SIZE);
 
    public static void main(String[] args) throws IOException {
        NioClient nioClient = new NioClient();
 
        //終端監聽(tīng)用戶(hù)輸入
        new Thread(nioClient::terminal).start();
 
        //這個(gè)方法是阻塞的，要放在最后
        nioClient.start();
    }
 
    public NioClient() throws IOException {
        selector = Selector.open();
        SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress(InetAddress.getLocalHost(), NioClient.PORT));
        socketChannel.configureBlocking(false);
        socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);
    }
 
    public void start() throws IOException {
        while (selector.select() > 0) {
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            while (iterator.hasNext()) {
                SelectionKey selectionKey = iterator.next();
                //拿到selectionKey后要刪除，否則會(huì )重復處理
                iterator.remove();
                if(selectionKey.isReadable()) {
                    handleRead(selectionKey);
                }
 
                //只要連接成功，selectionKey.isWritable()一直為true
                if(selectionKey.isWritable()) {
                    handleWrite(selectionKey);
                }
            }
        }
    }
 
    /**
     * 監聽(tīng)寫(xiě)操作
     */
    private void handleWrite(SelectionKey selectionKey) throws IOException {
        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
 
        // writeBuffer有數據就直接寫(xiě)入，因為另開(kāi)了線(xiàn)程監聽(tīng)用戶(hù)讀取，所以要上鎖
        synchronized (writeBuffer) {
            writeBuffer.flip();
            while (writeBuffer.hasRemaining()) {
                socketChannel.write(writeBuffer);
            }
            writeBuffer.compact();
        }
 
    }
 
    /**
     * 監聽(tīng)讀操作
     */
    private void handleRead(SelectionKey selectionKey) throws IOException {
        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
        readBuffer.clear();
        socketChannel.read(readBuffer);
 
        readBuffer.flip();
        String res = StandardCharsets.UTF_8.decode(readBuffer).toString();
        System.out.println("收到服務(wù)器發(fā)來(lái)的消息： " + res);
        readBuffer.clear();
    }
 
    /**
     * 監聽(tīng)終端的輸入
     */
    private void terminal() {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        try {
            String msg;
            while ((msg = bufferedReader.readLine()) != null) {
                synchronized (writeBuffer) {
                    writeBuffer.put((msg + "\r\n").getBytes(StandardCharsets.UTF_8));
                }
            }
        }catch (Exception e) {
            e.printStackTrace();
        }
 
    }
 
}

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