Socket编程

修娇花 · · ·

BIO模式

Server端

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
    public static void main(String[] args) throws IOException {
        System.out.println("---------------1.服务端启动 , 等待连接------------- ");
        // 1.创建 ServerSocket对象，绑定端口，开始等待连接
        ServerSocket ss = new ServerSocket(44444);
        // 2.接收连接accept方法，返回socket对象
        Socket server = ss.accept();
        // 3.通过socket获取输入流
        InputStream is = server.getInputStream();
        // 4.一次性读取数据
        // 4.1 创建字节数组
        byte[] b = new byte[1024];
        // 4.2 读取到字节数组中
        int len = is.read(b);
        // 4.3 解析数组，打印字符串信息
        String msg = new String(b, 0, len);
        System.out.println(msg);

        // 回写数据==========================================
        OutputStream os = server.getOutputStream();
        os.write("--------------4.这是服务端回写客户端的数据---------------".getBytes());

        // 5. 关闭资源
        os.close();
        is.close();
        server.close();
    }
}

Client端

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
public class Client {
    public static void main(String[] args) throws IOException {
        System.out.println("-----------2.这是客户端，发送数据-------------");
        // 1.创建socket（ip，port），确定连接到哪里
        Socket client = new Socket("localhost", 44444);
        // 2.获取流对象，输出流
        OutputStream os = client.getOutputStream();
        // 3.写出数据
        os.write("----------3.我是客户端向服务端写的数据---------".getBytes());

        // 读取数据=================================
        InputStream is = client.getInputStream();
        byte[] b = new byte[1024];
        int len = is.read(b);
        System.out.println(new String(b,0,len));

        // 4.关闭资源
        is.close();
        os.close();
        client.close();
    }
}

NIO模式

Server端

package leetcode;

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.Calendar;
import java.util.Iterator;

public class Server {
    public static void main(String[] args) throws IOException {
        try {
            //服务初始化
            ServerSocketChannel serverSocket = ServerSocketChannel.open();
            //设置为非阻塞
            serverSocket.configureBlocking(false);
            //绑定端口
            serverSocket.bind(new InetSocketAddress("localhost", 9999));
            //注册OP_ACCEPT事件（即监听该事件，如果有客户端发来连接请求，则该键在select()后被选中）
            Selector selector = Selector.open();
            serverSocket.register(selector, SelectionKey.OP_ACCEPT);
            Calendar ca = Calendar.getInstance();
            System.out.println("服务端开启了");
            System.out.println("=========================================================");
            //轮询服务
            while (true) {
                //选择准备好的事件
                selector.select();
                //已选择的键集
                Iterator<SelectionKey> it = selector.selectedKeys().iterator();
                //处理已选择键集事件
                while (it.hasNext()) {
                    SelectionKey key = it.next();
                    //处理掉后将键移除，避免重复消费(因为下次选择后，还在已选择键集中)
                    it.remove();
                    //处理连接请求
                    if (key.isAcceptable()) {
                        //处理请求
                        SocketChannel socket = serverSocket.accept();
                        socket.configureBlocking(false);
                        //注册read，监听客户端发送的消息
                        socket.register(selector, SelectionKey.OP_READ);
                        //keys为所有键，除掉serverSocket注册的键就是已连接socketChannel的数量
                        String message = "连接成功 你是第" + (selector.keys().size() - 1) + "个用户";
                        //向客户端发送消息
                        socket.write(ByteBuffer.wrap(message.getBytes()));
                        InetSocketAddress address = (InetSocketAddress) socket.getRemoteAddress();
                        //输出客户端地址
                        System.out.println(ca.getTime() + "\t" + address.getHostString() +
                                ":" + address.getPort() + "\t");
                        System.out.println("客戶端已连接");
                        System.out.println("=========================================================");
                    }

                    if (key.isReadable()) {
                        SocketChannel socket = (SocketChannel) key.channel();
                        InetSocketAddress address = (InetSocketAddress) socket.getRemoteAddress();
                        System.out.println(ca.getTime() + "\t" + address.getHostString() +
                                ":" + address.getPort() + "\t");
                        ByteBuffer bf = ByteBuffer.allocate(1024 * 4);
                        int len = 0;
                        byte[] res = new byte[1024 * 4];
                        //捕获异常，因为在客户端关闭后会发送FIN报文，会触发read事件，但连接已关闭,此时read()会产生异常
                        try {
                            while ((len = socket.read(bf)) != 0) {
                                bf.flip();
                                bf.get(res, 0, len);
                                System.out.println(new String(res, 0, len));
                                bf.clear();
                            }
                            System.out.println("=========================================================");
                        } catch (IOException e) {
                            //客户端关闭了
                            key.cancel();
                            socket.close();
                            System.out.println("客戶端已断开");
                            System.out.println("=========================================================");
                        }
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("服务器异常，即将关闭..........");
            System.out.println("=========================================================");
        }
    }
}

Client端

package leetcode;

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.SocketChannel;
import java.util.Calendar;
import java.util.Iterator;
import java.util.Set;

public class Client {
    public static void main(String[] args) throws IOException {
        try {
            //初始化客户端
            SocketChannel socket = SocketChannel.open();
            socket.configureBlocking(false);
            Selector selector = Selector.open();
            //注册连接事件
            socket.register(selector, SelectionKey.OP_CONNECT);
            //发起连接
            socket.connect(new InetSocketAddress("localhost", 9999));
            //开启控制台输入监听
            new ChatThread(selector, socket).start();
            Calendar ca = Calendar.getInstance();
            //轮询处理
            while (true) {
                if (socket.isOpen()) {
                    //在注册的键中选择已准备就绪的事件
                    selector.select();
                    //已选择键集
                    Set<SelectionKey> keys = selector.selectedKeys();
                    Iterator<SelectionKey> iterator = keys.iterator();
                    //处理准备就绪的事件
                    while (iterator.hasNext()) {
                        SelectionKey key = iterator.next();
                        //删除当前键，避免重复消费
                        iterator.remove();
                        //连接
                        if (key.isConnectable()) {
                            //在非阻塞模式下connect也是非阻塞的，所以要确保连接已经建立完成
                            while (!socket.finishConnect()) {
                                System.out.println("连接中");
                            }
                            socket.register(selector, SelectionKey.OP_READ);
                        }
                        //控制台监听到有输入，注册OP_WRITE,然后将消息附在attachment中
                        if (key.isWritable()) {
                            //发送消息给服务端
                            socket.write((ByteBuffer) key.attachment());
                            /*
	                            已处理完此次输入，但OP_WRITE只要当前通道输出方向没有被占用
	                            就会准备就绪，select()不会阻塞（但我们需要控制台触发,在没有输入时
	                            select()需要阻塞），因此改为监听OP_READ事件，该事件只有在socket
	                            有输入时select()才会返回。
                            */
                            socket.register(selector, SelectionKey.OP_READ);
                            System.out.println("==============" + ca.getTime() + " ==============");
                        }
                        //处理输入事件
                        if (key.isReadable()) {

                            ByteBuffer byteBuffer = ByteBuffer.allocate(1024 * 4);
                            int len = 0;
                            //捕获异常，因为在服务端关闭后会发送FIN报文，会触发read事件，但连接已关闭,此时read()会产生异常
                            try {

                                if ((len = socket.read(byteBuffer)) > 0) {
                                    System.out.println("接收到來自服务器的消息\t");
                                    System.out.println(new String(byteBuffer.array(), 0, len));
                                }
                            } catch (IOException e) {
                                System.out.println("服务器异常，请联系客服人员!正在关闭客户端.........");
                                key.cancel();
                                socket.close();
                            }
                            System.out.println("=========================================================");
                        }
                    }
                } else {
                    break;
                }
            }

        } catch (IOException e) {
            System.out.println("客户端异常，请重启！");
        }
    }
}

ChatThread类（Thread）

package leetcode;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Scanner;

public class ChatThread extends Thread {

    private Selector selector;
    private SocketChannel socket;

    public ChatThread(Selector selector, SocketChannel socket) {
        super();
        this.selector = selector;
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            //等待连接建立
            Thread.sleep(500);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入您要发送给服务端的消息");
        System.out.println("=========================================================");
        while (scanner.hasNextLine()) {
            String s = scanner.nextLine();
            try {
                //用户已输入，注册写事件，将输入的消息发送给客户端
                socket.register(selector, SelectionKey.OP_WRITE, ByteBuffer.wrap(s.getBytes()));
                //唤醒之前因为监听OP_READ而阻塞的select()
                selector.wakeup();
            } catch (ClosedChannelException e) {
                e.printStackTrace();
            }
        }
    }
}

Q.E.D.

Docker底层原理（更新ing）

Java面经（更新ing）

修娇花

修娇花

在读程序猿+指弹发烧友+力量举、街头健身爱好者。

你好，朋友！

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