java socket 模拟im 即时通讯

Posted 2020-09-03 高因咖啡

自己想了一下怎么实现,就写了,没有深究是否合理.更多处理没有写下去,例如收件人不在线,应该保存在数据库,等下一次连接的时候刷新map,再把数据发送过去,图片发送也没有做,也没有用json格式

socket很奇怪,我用客户端连接上了服务器,没有发送消息的情况下,断开电脑网络,是不会出现问题,然后在把电脑网络连接上,通讯依然正常,正常断开也不出问题,但是用idea直接按stop键,那么服务端就会出问题了,读取事件会一直为true,造成死循环,消耗CPU,所以必须要判断一下客户端连接是否断开了

 

只需要把客户端代码启动几个,修改一些userName以及收件人,就可以测试,实现类似QQ微信即时通讯,聊天功能

 

 

服务端代码

package serversocketchannel;

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.nio.charset.Charset;
import java.util.Iterator;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 
 * @author ZhenWeiLai
 *
 */
public class ServerSocketChannelNonBlocking {
    private static ServerSocketChannel serverSocketChannel = null;
    private static Charset charset = Charset.forName("GBK");//设置编码集,用于编码,解码
    private static Selector selector = null;
    //保存客户端的map
    private static final ConcurrentHashMap<String,SocketChannel> clientSockets = new ConcurrentHashMap<>();
    static{
        try {
            serverSocketChannel = ServerSocketChannel.open();
            serverSocketChannel.socket().setReuseAddress(true);
            serverSocketChannel.socket().bind(new InetSocketAddress(8000));
            serverSocketChannel.configureBlocking(false);//设置为非阻塞
            selector = Selector.open();//实例化一个选择器
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
            service();
    }
    
    private static void service(){
        SocketChannel clientChannel = null;
        SelectionKey selectionKey = null;
        SocketChannel targetChannel = null;
        try {
            serverSocketChannel.register(selector,SelectionKey.OP_ACCEPT);//服务端监听连接
            while(true){
                selector.select();//阻塞至有新的连接就开始处理
                Iterator<SelectionKey> selectionKeys = selector.selectedKeys().iterator();
                while(selectionKeys.hasNext()){
                    selectionKey = selectionKeys.next();
                    if(selectionKey.isAcceptable()){//如果事件是连接事件
                        ServerSocketChannel serverChannel = (ServerSocketChannel)selectionKey.channel();//获取事件绑定的channel
                        clientChannel = serverChannel.accept();//连接获取带客户端信息的socketChannel
                        clientChannel.configureBlocking(false);//客户设置为非阻塞,因为非阻塞才支持选择器.避免盲等浪费资源
                        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);//作为每一个客户端的附件缓冲器
                        /**
                         * 只监听读事件,这里千万别监听写事件,因为只要连接有效,那么写事件会一直为true,导致死循环,很耗资源
                         * 可以跟serverSocket用同一个选择器,因为绑定的channel不同
                         */
                        clientChannel.register(selector,SelectionKey.OP_READ,byteBuffer);
                    }else if(selectionKey.isReadable()){//只要有客户端写入,那么就可以处理
                        //获取客户端附件,也就是写入的数据
                        ByteBuffer byteBuffer = (ByteBuffer)selectionKey.attachment();
                        //从selectionKey获取客户端的channel
                        SocketChannel socketChannel = (SocketChannel)selectionKey.channel();
                        //把附件读出,解码为字符串
                        String msg = read(socketChannel,byteBuffer);
                        //这里用了->分割收件人,->后面跟着的字符串是收件人
                        if(msg.indexOf("->")!=-1){
                            //内容
                            String content = msg.substring(0,msg.lastIndexOf("->"));
                            //从map里获取收件人的socket
                            targetChannel = clientSockets.get(msg.substring(msg.lastIndexOf("->")+2));
                            //实例化一个缓冲区,用来写出到收件人的socketChannel
                            ByteBuffer temp = ByteBuffer.allocate(1024);
                            temp.put(charset.encode(content));
                            //写出
                            handleWrite(targetChannel,temp);
                        }else{
                            //如果内容没有收件人,那么视为第一次连接,客户端发过来的userName,作为KEY存入MAP
                            clientSockets.put(msg,socketChannel);
                        }
                    }
                    selectionKeys.remove();
                }
            }
        } catch (IOException e) {
            try {
                if(selectionKey!=null)selectionKey.cancel();
                if(clientChannel!=null){
                    clientChannel.shutdownInput();
                    clientChannel.shutdownOutput();
                    clientChannel.close();
                }
                if(targetChannel!=null){
                    targetChannel.shutdownInput();
                    targetChannel.shutdownOutput();
                    targetChannel.close();
                }
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            e.printStackTrace();
        }

    }
    
    private static String read(SocketChannel socketChannel,ByteBuffer byteBuffer){
        //重置position limit为写入做准备
        byteBuffer.clear();
        try {
            int flag =socketChannel.read(byteBuffer);
            //判断客户端是否断开连接
            if(flag==-1){
                //如果客户端无故断开,一定要关闭,否则读取事件一直为true造成死循环,非常耗资源
                socketChannel.close();
            }
        } catch (IOException e) {
            try {
                socketChannel.close();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
            e.printStackTrace();
        }
        //position =0 limit等于有效下标,为写出做准备
        byteBuffer.flip();
        return charset.decode(byteBuffer).toString();
    }
    
    //写出
    private static void handleWrite(SocketChannel socketChannel,ByteBuffer byteBuffer){
        synchronized (byteBuffer) {
            byteBuffer.flip();
            try {
                socketChannel.write(byteBuffer);
            } catch (IOException e) {
                try {
                    socketChannel.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
                e.printStackTrace();
            }
        }
    }
}

客户端代码

package socketchannel;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
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.nio.charset.Charset;
import java.util.Iterator;

/**
 * Created by lzw on 17-2-28.
 */
public class SocketChannelNonBlockingClient {
    private static Charset charset = Charset.forName("GBK");
    private static ByteBuffer receiveBuffer = ByteBuffer.allocate(10240);
    private static ByteBuffer sendBuffer = ByteBuffer.allocate(10240);
    private static SocketChannel socketChannel = null;
    private static Selector selector = null;
    private static String userName = "client1";//客户端名
    private static String targetName = "client2";//收件人名

    public static void main(String[] args) {
        try {
            socketChannel = SocketChannel.open();
            //连接到服务端
            SocketAddress socketAddress = new InetSocketAddress("19.95.103.112",8000);
            selector = Selector.open();//实例化一个选择器
            socketChannel.configureBlocking(false);//设置为非阻塞
            //先监听一个连接事件
            socketChannel.register(selector,SelectionKey.OP_CONNECT);
            //连接
            socketChannel.connect(socketAddress);
            //jdk 1.8的lambda表达式，用一个线程监控控制台输入
            new Thread(()->{
                    try {
                        receiveFromUser();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
            }).start();

            talk();

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    private static void talk(){
        try {
            while(true){
                selector.select();//阻塞直到连接事件
                Iterator<SelectionKey> readyKeys = selector.selectedKeys().iterator();
               while(readyKeys.hasNext()){
                    SelectionKey key =readyKeys.next();
                    if(key.isConnectable()){
                        //非阻塞的情况下可能没有连接完成，这里调用finishConnect阻塞至连接完成
                        socketChannel.finishConnect();
                        //连接完成以后，先发送自己的userName以便保存在服务端的客户端map里面
                        synchronized (sendBuffer){
                            SocketChannel socketChannel1 = (SocketChannel)key.channel();
                            sendBuffer.clear();
                            sendBuffer.put(charset.encode(userName));
                            send(socketChannel1);
                            socketChannel.register(selector,SelectionKey.OP_READ);//仅监听一个读取事件
                        }

                    }else if(key.isReadable()){
                        //处理读事件
                        receive(key);
                    }
                    readyKeys.remove();
                }
            }
        } catch (ClosedChannelException e) {
            try {
                socketChannel.close();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    /**
     * 从控制台获取用户输入
     * @throws IOException
     */
    private static void receiveFromUser() throws IOException{
        //阻塞直到控制台有输入
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        for(String msg = br.readLine();msg!=null&&!msg.equals("bye");msg = br.readLine()){
            //同步锁避免线程竞争
            synchronized (sendBuffer) {
                sendBuffer.clear();
                //编码
                sendBuffer.put(charset.encode(msg));
                //分割副
                sendBuffer.put(charset.encode("->"));
                //目标名
                sendBuffer.put(charset.encode(targetName));
                send(socketChannel);
            }
        }
    }
    /**
     * 接收服务端的数据
     * @param key
     */
    private static void receive(SelectionKey key) throws IOException {
        //获取服务端的channel
        SocketChannel channel = (SocketChannel) key.channel();
        //为写入缓冲器做准备position=0,limit=capacity
            receiveBuffer.clear();
            //从服务端的channel把数据读入缓冲器
            channel.read(receiveBuffer);
            //position=0,limit=有效下标最后一位
            receiveBuffer.flip();
            //解码
            String msg = charset.decode(receiveBuffer).toString();
            //输出到控制台
            System.out.println(msg);
    }

    /**
     * 发送到服务端
     */
    private static void send(SocketChannel sendChannel) throws IOException {
            if(sendBuffer.remaining()!=0){
                synchronized (sendBuffer){
                    sendBuffer.flip();
                    sendChannel.write(sendBuffer);
                }
            }
    }
}