即时通讯

public class ClientDemo {
    public static void main(String[] args) throws Exception{
        System.out.println("=====客户端启动=====");
        Socket socket = new Socket("127.0.0.1",9999);

        new Shou(socket).start();

        OutputStream os = socket.getOutputStream();

        PrintStream ps = new PrintStream(os);
        Scanner sc = new Scanner(System.in);
        while(true){
            System.out.println("请说");
            String rs = sc.nextLine();
            ps.println(rs);
        }

    }
}
class DuXiaoxi extends Thread {
    private Socket socket;

    public DuXiaoxi(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            InputStream is = socket.getInputStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(is));

            String rs;
            while ((rs = br.readLine()) != null){
                System.out.println(socket.getRemoteSocketAddress() +"说了:"+rs);
            }
        } catch (IOException e) {
            System.out.println("您被踢出群聊");
        }
    }
}
===

public class ServerDemo {
    public static ArrayList<Socket> Allonlinesocket = new ArrayList<>();
    public static void main(String[] args) {
        try {
            System.out.println("=====服务端启动=====");
            ServerSocket serverSocket = new ServerSocket(9999);//这个不能放循环里面


            while (true) {
                Socket socket = serverSocket.accept();

                Allonlinesocket.add(socket);


                new MyThead(socket).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class MyThead extends Thread{
    private Socket socket;

    public MyThead(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {

        try {
            InputStream is = socket.getInputStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(is));

            String rs;
            while ((rs = br.readLine()) != null){
                System.out.println(socket.getRemoteSocketAddress() +"说了:"+rs);
                sendMsgToAll(rs);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    private void sendMsgToAll(String msg) throws Exception{
        for (Socket socket : ServerDemo.Allonlinesocket) {
            OutputStream outputStream = socket.getOutputStream();
            PrintStream ps = new PrintStream(outputStream);
            ps.print(msg);
            ps.flush();
        }
    }
}