import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketAddress;


public class ServerDemo {


    /** 若采用 IPv4 的地址结构搭建服务，使用 IPV4_HOST */
    public static final String IPV4_HOST = "0.0.0.0";


    /** 若采用 IPv6 的地址结构搭建服务，使用 IPV6_HOST */
    public static final String IPV6_HOST = "::";


    public static void main(String[] args) {
        int serverPort = 10000;
        try (ServerSocket serverSocket = new ServerSocket()) {
            // 设置地址复用
            serverSocket.setReuseAddress(true);
            // 绑定服务器地址和端口，这里使用 IPv4
            serverSocket.bind(new InetSocketAddress(InetAddress.getByName(IPV4_HOST), serverPort));
            System.out.println("Server is listening on port " + serverPort);


            while (true) {
                // 接受客户端连接
                Socket clientSocket = serverSocket.accept();
                System.out.println("New client connected: " + clientSocket.getRemoteSocketAddress());


                // 处理客户端请求
                handleClientRequest(clientSocket);
            }
        } catch (IOException e) {
            System.err.println("Failed to create server socket: " + e.getMessage());
        }
    }


    /**
     * 处理函数，具体业务具体实现，这里只做为示例
     * 此函数的作用是将 client 的输入原封不动的返回给 client
     */
    private static void handleClientRequest(Socket clientSocket) {
        try (InputStream inputStream = clientSocket.getInputStream();
             OutputStream outputStream = clientSocket.getOutputStream()) {


            // 读取客户端发来的数据
            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                // 将接收到的数据原样回复给客户端
                outputStream.write(buffer, 0, bytesRead);
            }


        } catch (IOException e) {
            // 当客户端断开连接后
            System.err.println("Failed to handle client request: " + e.getMessage());
        } finally {
            try {
                clientSocket.close();
            } catch (IOException e) {
                System.err.println("Failed to close client socket: " + e.getMessage());
            }
        }
    }
}