tcp nio服务端和客户端例子

以下是一个使用Java NIO实现的TCP Server和Client的示例代码：

TCP Server:

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;

public class TCPServer {
    private Selector selector;
    private ByteBuffer buffer = ByteBuffer.allocate(1024);
    
    public TCPServer(int port) throws IOException {
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.configureBlocking(false);
        serverSocketChannel.socket().bind(new InetSocketAddress(port));
        
        selector = Selector.open();
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        
        System.out.println("Server started on port " + port);
    }
    
    private void start() throws IOException {
        while (true) {
            selector.select();
            Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
            
            while (keys.hasNext()) {
                SelectionKey key = keys.next();
                keys.remove();
                
                if (!key.isValid()) {
                    continue;
                }
                
                if (key.isAcceptable()) {
                    accept(key);
                } else if (key.isReadable()) {
                    read(key);
                } else if (key.isWritable()) {
                    write(key);
                }
            }
        }
    }
    
    private void accept(SelectionKey key) throws IOException {
        ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel();
        SocketChannel socketChannel = serverSocketChannel.accept();
        socketChannel.configureBlocking(false);
        socketChannel.register(selector, SelectionKey.OP_READ);
        System.out.println("Accepted connection from " + socketChannel.getRemoteAddress());
    }
    
    private void read(SelectionKey key) throws IOException {
        SocketChannel socketChannel = (SocketChannel) key.channel();
        buffer.clear();
        int bytesRead = socketChannel.read(buffer);
        if (bytesRead == -1) {
            socketChannel.close();
            System.out.println("Connection closed by " + socketChannel.getRemoteAddress());
            return;
        }
        buffer.flip();
        byte[] data = new byte[buffer.limit()];
        buffer.get(data);
        System.out.println("Received data from " + socketChannel.getRemoteAddress() + ": " + new String(data));
        socketChannel.register(selector, SelectionKey.OP_WRITE, data);
    }
    
    private void write(SelectionKey key) throws IOException {
        SocketChannel socketChannel = (SocketChannel) key.channel();
        byte[] data = (byte[]) key.attachment();
        ByteBuffer byteBuffer = ByteBuffer.wrap(data);
        socketChannel.write(byteBuffer);
        System.out.println("Sent data to " + socketChannel.getRemoteAddress() + ": " + new String(data));
        socketChannel.register(selector, SelectionKey.OP_READ);
    }
    
    public static void main(String[] args) throws IOException {
        TCPServer server = new TCPServer(8080);
        server.start();
    }
}

TCP Client:

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;

public class TCPClient {
    private SocketChannel socketChannel;
    private ByteBuffer buffer = ByteBuffer.allocate(1024);
    
    public TCPClient(String host, int port) throws IOException {
        socketChannel = SocketChannel.open();
        socketChannel.configureBlocking(false);
        socketChannel.connect(new InetSocketAddress(host, port));
    }
    
    private void start() throws IOException {
        while (!socketChannel.finishConnect()) {
            // Wait for connection to be established
        }
        
        System.out.println("Connected to server " + socketChannel.getRemoteAddress());
        
        String message = "Hello, server!";
        buffer.put(message.getBytes());
        buffer.flip();
        socketChannel.write(buffer);
        System.out.println("Sent data to server: " + message);
        
        buffer.clear();
        int bytesRead = socketChannel.read(buffer);
        if (bytesRead == -1) {
            socketChannel.close();
            System.out.println("Connection closed by server");
            return;
        }
        buffer.flip();
        byte[] data = new byte[buffer.limit()];
        buffer.get(data);
        System.out.println("Received data from server: " + new String(data));
        
        socketChannel.close();
    }
    
    public static void main(String[] args) throws IOException {
        TCPClient client = new TCPClient("localhost", 8080);
        client.start();
    }
}