如何使用java实现客户端与服务器

小编给大家分享一下如何使用java实现客户端与服务器，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！

Java可以用来干什么

Java主要应用于：1. web开发；2. Android开发；3. 客户端开发；4. 网页开发；5. 企业级应用开发；6. Java大数据开发；7.游戏开发等。

运行效果

开启多个客户端

服务端效果：

客户端效果：

当一个客户端断开连接：

代码

因为代码中有注释，我就直接贴上来了

服务端：

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 {        private static final int PORT = 8081;        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 {        //创建一个服务端channel        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();         //设置为非阻塞        serverSocketChannel.configureBlocking(false);         //获取服务器socket        ServerSocket socket = serverSocketChannel.socket();        //绑定ip和端口        socket.bind(new InetSocketAddress(NioServer.PORT));         //创建多路复用选择器，并保持打开状态，直到close        selector = Selector.open();         //将服务器管道注册到selector上，并监听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，直到至少有一个客户端连接。        while (selector.select() > 0) {            //SelectionKey是channel想Selector注册的令牌，可以通过chancel取消（不是立刻取消，会放进一个cancel list里面，下一次select时才会把它彻底删除）            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();            while (iterator.hasNext()) {                SelectionKey selectionKey = iterator.next();                iterator.remove();                //当这个key的channel已经准备好接收套接字连接                if(selectionKey.isAcceptable()) {                    connectHandle(selectionKey);                }                 //当这个key的channel已经准备好读取数据时                if(selectionKey.isReadable()) {                    readHandle(selectionKey);                }            }        }    }         private void connectHandle(SelectionKey selectionKey) throws IOException {        //注意，服务端用的是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("客户端连接成功，当前总数：" + (++count));         writeBuffer.clear();        writeBuffer.put("连接成功".getBytes(StandardCharsets.UTF_8));        writeBuffer.flip();        socketChannel.write(writeBuffer);    }         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("收到客户端消息: " + 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("客户端断开了连接~~");            count--;        }    }}

客户端

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();         //终端监听用户输入        new Thread(nioClient::terminal).start();         //这个方法是阻塞的，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后要删除，否则会重复处理                iterator.remove();                if(selectionKey.isReadable()) {                    handleRead(selectionKey);                }                 //只要连接成功，selectionKey.isWritable()一直为true                if(selectionKey.isWritable()) {                    handleWrite(selectionKey);                }            }        }    }         private void handleWrite(SelectionKey selectionKey) throws IOException {        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();         // writeBuffer有数据就直接写入，因为另开了线程监听用户读取，所以要上锁        synchronized (writeBuffer) {            writeBuffer.flip();            while (writeBuffer.hasRemaining()) {                socketChannel.write(writeBuffer);            }            writeBuffer.compact();        }     }         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("收到服务器发来的消息： " + res);        readBuffer.clear();    }         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();        }     } }

以上是“如何使用java实现客户端与服务器”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注编程网服务器频道！