1.服务端

import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;

public class TcpServer {

    public static void main(String[] args) throws Exception{
        List<Socket> list = new ArrayList<>();
        try{
            System.out.println("服务端已就绪。。。");
            ServerSocket serverSocket = new ServerSocket(8088);
            while (true){
                Socket socket = serverSocket.accept();
                list.add(socket);
                InputStream inputStream = socket.getInputStream();
                byte[] bytes = new byte[1024];
                inputStream.read(bytes);
                System.out.println("新用户上线,端口号为:" + socket.getPort() + ",用户信息：" + (new String(bytes)) + "，当前用户数：" + list.size());
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

2.客户端

import java.io.OutputStream;
import java.net.Socket;

public class TcpClient {

    public static void main(String[] args){

        try{
            Socket socket = new Socket("127.0.0.1",8088);
            OutputStream outputStream = socket.getOutputStream();
            outputStream.write("qqid:2370775541".getBytes());
            outputStream.close();
        }catch (Exception e){
            e.printStackTrace();
        }

    }
}