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Netty学习笔记:二、NIO网络应用实例-群聊系统

实例要求:

  1. 编写一个NIO群聊系统,实现服务器端和多个客户端之间的数据简单通讯(非阻塞);
  2. 实现多人群聊;
  3. 服务器端:可以监测用户上线、离线,并实现消息转发功能;
  4. 客户端:通过channel可以无阻塞发送消息给其他所有用户,同时接受其他用户发送的消息;
  5. 目的:进一步理解NIO非阻塞网络编程机制;

代码演示:

服务端代码:

package com.study.demo.groupchat;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;

public class GroupChatServer {

    //定义属性

    private Selector selector;
    private ServerSocketChannel listenChannel;
    private static final int PORT = 6667;

    //构造器
    //初始化工作
    public GroupChatServer() {
        try {
            //得到选择器
            selector = Selector.open();
            //ServerSocketChannel
            listenChannel = ServerSocketChannel.open();
            //绑定端口
            listenChannel.socket().bind(new InetSocketAddress(PORT));
            //设置非阻塞模式
            listenChannel.configureBlocking(false);
            //将该listenChannel 注册到selector
            listenChannel.register(selector, SelectionKey.OP_ACCEPT);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //监听
    public void listen() {
        try {
            while (true) {
                int count = selector.select();
                if (count > 0) {//有事件需要处理
                    //遍历得到selectionKey集合
                    Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                    while (iterator.hasNext()) {
                        //获取selectionKey
                        SelectionKey key = iterator.next();

                        //监听accept
                        if(key.isAcceptable()) {
                            SocketChannel sc = listenChannel.accept();
                            sc.configureBlocking(false);
                            //将该sc 注册到selector
                            sc.register(selector, SelectionKey.OP_READ);

                            System.out.println(sc.getRemoteAddress() + "上线了");
                        }

                        //通道发送read事件,即通道是可读的操作
                        if(key.isReadable()) {
                            readDate(key);
                        }
                        //把当前的key删除 防止重复操作
                        iterator.remove();

                    }
                } else {
                    System.out.println("等等.....");
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //读取客户端消息
    private void readDate(SelectionKey key) {
        //定一个SocketChannel
        SocketChannel channel = null;
        try {
            //得到channel
            channel = (SocketChannel) key.channel();

            //创建一个buffer
            ByteBuffer buffer = ByteBuffer.allocate(1024);

            int count = channel.read(buffer);
            if (count > 0) {
                //把缓存区的数据转成字符串
                String msg = new String(buffer.array());
                //输出消息
                System.out.println("from 客户端:" + msg);

                //向其他的客户端转发消息,再写一个方法来处理
                sendInfoToOtherClients(msg, channel);
            }
        } catch (IOException e) {
            try {
                System.out.println(channel.getRemoteAddress() + " 离线了");
                //取消注册
                key.cancel();
                //关闭通道
                channel.close();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
            e.printStackTrace();
        }
    }

    //转发给其他客户端(通道)
    private void sendInfoToOtherClients(String msg, SocketChannel self) throws IOException {
        System.out.println("服务器转发消息中...");
        //遍历 所有注册到selector上的SocketChannel,并排除self
        for (SelectionKey key : selector.keys()) {
            //通过key 获取对应的SocketChannel
            Channel targetChannel = key.channel();

            //排除自己
            if(targetChannel instanceof SocketChannel && targetChannel != self) {
                //转型
                SocketChannel dest = (SocketChannel) targetChannel;
                //将msg存储到buffer
                ByteBuffer buffer = ByteBuffer.wrap(msg.getBytes());

                //将buffer的数据写入通道
                dest.write(buffer);
            }
        }
    }


    public static void main(String[] args) {
        //创建一个服务器对象
        GroupChatServer server = new GroupChatServer();
        server.listen();
    }

}

 客户端代码:

package com.study.demo.groupchat;

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.Iterator;
import java.util.Scanner;

public class GroupChatClient {

    //定义属性
    private final String HOST = "127.0.0.1";
    private final int PORT = 6667;
    private Selector selector;
    private SocketChannel socketChannel;
    private String username;

    //构造器
    public GroupChatClient() throws IOException {
        selector = Selector.open();

        //连接服务器
        socketChannel = socketChannel.open(new InetSocketAddress(HOST, PORT));

        //设置非阻塞
        socketChannel.configureBlocking(false);

        //将channel注册到selector
        socketChannel.register(selector, SelectionKey.OP_READ);
        //得到username
        username = socketChannel.getLocalAddress().toString().substring(1);
        System.out.println(username + " is ok ...");
    }

    //向服务器发送消息
    public void sendInfo(String info) {
        info = username + " 说:" + info;
        try {
            socketChannel.write(ByteBuffer.wrap(info.getBytes()));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    //读取从服务器端回复的消息

    public void readInfo() {
        try {
            int readChannels = selector.select();
            if (readChannels > 0) {//有可用的通道
                Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                while (iterator.hasNext()) {

                    SelectionKey key = iterator.next();

                    if (key.isReadable()) {
                        //得到相关的通道
                        SocketChannel sc = (SocketChannel) key.channel();
                        //得到一个buffer
                        ByteBuffer buffer = ByteBuffer.allocate(1024);
                        //读取
                        sc.read(buffer);

                        //把读取的缓冲区的数据转成字符串
                        String msg = new String(buffer.array());
                        System.out.println(msg.trim());

                    }
                }
                iterator.remove();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws IOException {
        //启动客户端
        GroupChatClient chatClient = new GroupChatClient();

        //启动一个线程 每隔3秒 读取从服务器发送的数据
        new Thread() {
            @Override
            public void run() {
                while (true) {
                    chatClient.readInfo();
                    try {
                        Thread.currentThread().sleep(3000);
                    }  catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }.start();

        //发送数据给服务端
        Scanner scanner = new Scanner(System.in);

        while (scanner.hasNextLine()) {
            String s = scanner.nextLine();
            chatClient.sendInfo(s);
        }

    }

}

演示效果:

 server服务端输出:

/127.0.0.1:58743上线了
/127.0.0.1:56568上线了
/127.0.0.1:53544上线了
from 客户端:127.0.0.1:58743 说:我是 743                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
服务器转发消息中...
from 客户端:127.0.0.1:56568 说:我是 568                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
服务器转发消息中...
from 客户端:127.0.0.1:53544 说:我是544                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
服务器转发消息中...
/127.0.0.1:53544 离线了

client1客户端输出:

127.0.0.1:58743 is ok ...
我是 743
127.0.0.1:56568 说:我是 568
127.0.0.1:53544 说:我是544

 clien2客户端输出:

127.0.0.1:56568 is ok ...
127.0.0.1:58743 说:我是 743
我是 568
127.0.0.1:53544 说:我是544


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