import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;
/**1.創(chuàng)建服務(wù)器 綁定端口號(hào)
 * 2.在循環(huán)中 調(diào)用accept方法 重復(fù)監(jiān)聽連接過來的客戶端
 * 3.啟動(dòng)線程保持和多個(gè)客戶端連接
 * 4.在線程中 傳進(jìn)去對(duì)應(yīng)的socket 獲取輸入輸出流 實(shí)現(xiàn)和客戶端的雙向通訊
 * 5.創(chuàng)建客戶端對(duì)象 綁定服務(wù)器的IP地址和端口 讓客戶端去連接服務(wù)器
 * 6.利用客戶端輸入輸出流 跟服務(wù)端通訊
 * 7.在客戶端啟動(dòng)線程 一直讀取服務(wù)器發(fā)來的消息
 *
 */
public class MyServer {
    public static void main(String[] args){
        try {
            new MyServer().startServer();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    //啟動(dòng)服務(wù)器
    public void startServer() throws IOException {
        //創(chuàng)建服務(wù)器對(duì)象，并綁定監(jiān)聽器端口
        //端口取值范圍（2字節(jié)）：0~65535
        //知名端口：0~1024
        ServerSocket server=new ServerSocket(8888);
        System.out.println("服務(wù)端在8888端口監(jiān)聽器");
        //哈希表：保存一組映射關(guān)系：每個(gè)編號(hào)對(duì)應(yīng)唯一的socket
        //基本數(shù)據(jù)類型對(duì)應(yīng)的包裝類
        HashMap<Integer,Socket> mp=new HashMap<>();
        //每個(gè)鏈接過來的客戶端ID
        int ID=1;
        //重復(fù)監(jiān)聽連接這個(gè)服務(wù)器的客戶端
        while(true){
            //監(jiān)聽連接這個(gè)服務(wù)器的客戶端
            //該方法的返回的socket用來客戶端通信
            Socket socket=server.accept();
            //保存當(dāng)前對(duì)應(yīng)的數(shù)據(jù)
            mp.put(ID,socket);
            //利用線程保持和多個(gè)客戶端連接
            ServerThread st=new ServerThread(socket,mp,ID);
            new Thread(st).start();
            ID++;
        }
    }
}

 HashMap<Integer,Socket> mp=new HashMap<>();

new Thread(st).start();

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.util.Collection;
import java.util.HashMap;
public class ServerThread implements Runnable{
    //跟客戶端連接的套接字
    public Socket socket;
    public InputStream is;
    public OutputStream os;
    public HashMap<Integer,Socket> mp;
    public int ID;
    public ServerThread(Socket socket,HashMap<Integer,Socket> mp,int ID){
        this.socket=socket;
        this.mp=mp;
        try {
            os = socket.getOutputStream();
            is = socket.getInputStream();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        //發(fā)送客戶端上線消息
        sendMsg(ID+":客戶端上線..",os);
    }
    @Override
    public void run() {
        while(true) {
            try {
                //msg消息內(nèi)容:   目標(biāo)用戶:消息內(nèi)容
                String msg = readMsg();
                //對(duì)msg進(jìn)行解析：拆分
                // 字符串分割
                String[] msgArr = msg.split(":");
                System.out.println(msgArr[0] + ":" + msgArr[1]);
                if(msgArr[0].equals("g")){
                    Collection<Socket> values=mp.values();
                        for (Socket value : values) {
                            //不將消息發(fā)給自己
                            if(value != this.socket) {
                            System.out.println("值：" + value);
                            OutputStream output = value.getOutputStream();
                            sendMsg(msgArr[1], output);
                        }
                    }
                }else{
                    //根據(jù)目標(biāo)用戶（ID）從mp中找到對(duì)應(yīng)的socket(聊天對(duì)象）
                    int id = Integer.parseInt(msgArr[0]);  //字符串?dāng)?shù)字轉(zhuǎn)成int
                    Socket socket = mp.get(id);
                    //獲取該對(duì)象的輸出流，寫入數(shù)據(jù)
                    OutputStream output = socket.getOutputStream();
                    //把聊天內(nèi)容轉(zhuǎn)發(fā)給目標(biāo)用戶(聊天對(duì)象)
                    sendMsg(msgArr[1], output);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    //發(fā)送消息的方法
    public void sendMsg(String msg,OutputStream os){
        try {
            byte[] b = msg.getBytes();
            os.write(b);
            os.flush();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    //讀取消息的方法
    public String readMsg(){
        byte[] b = new byte[1024];  //最多讀取的消息長度
        try {
            is.read(b);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        // trim() 去掉字符尾部空格
        String s=new String(b);
        return s.trim();
    }
}

String[] msgArr = msg.split(":");
                System.out.println(msgArr[0] + ":" + msgArr[1]);

import java.util.Collection;
import java.util.HashMap;
public class HashMapTraversal {
    public static void main(String[] args) {
        HashMap<String, Integer> map = new HashMap<>();
        map.put("A", 1);
        map.put("B", 2);
        map.put("C", 3);
        Collection<Integer> values = map.values();
        for (Integer value : values) {
            System.out.println("Value: " + value);
        }
    }
}

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.util.Scanner;
public class Client {
    public static void main(String[] args){
        try {
            new Client().startClient();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    public InputStream is;
    public OutputStream os;
    //啟動(dòng)客戶端
    public void startClient() throws IOException{
        Socket client =new Socket("127.0.0.1",8888);
        os=client.getOutputStream();
        is=client.getInputStream();
        new Thread(()->{
            while(true){
                //讀取服務(wù)器消息
                String msg=readMsg();
                System.out.println(msg);
            }
        }).start();
        //發(fā)消息
        Scanner scanner=new Scanner(System.in);
        while(true){
            System.out.println("client:");
            String clientMsg=scanner.nextLine();
            sendMsg(clientMsg);
        }
    }
    //發(fā)送消息的方法
    public void sendMsg(String msg){
        try {
            os.write(msg.getBytes());
            os.flush();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    public String readMsg(){
        byte[] b=new byte[1024];
        try {
            //阻塞方法：一直等待讀取消息，如果沒有會(huì)一直等著
            is.read(b);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        //trim
        return new String(b).trim();
    }
}

        new Thread(()->{
            while(true){
                //讀取服務(wù)器消息
                String msg=readMsg();
                System.out.println(msg);
            }
        }).start();

 Scanner scanner=new Scanner(System.in);
        while(true){
            System.out.println("client:");
            String clientMsg=scanner.nextLine();
            sendMsg(clientMsg);
        }
    }