tcp服务端，时刻在线

C++ TCP 服务端和客户端通信的例子
在此基础上，将服务端改为时刻在线

#include <iostream>
#include <winsock2.h>
#include <Ws2tcpip.h> // for inet_ntop

#pragma comment(lib, "Ws2_32.lib")

#define PORT 8080

int main() {
    WSADATA wsaData;
    SOCKET serverSocket, newSocket;
    struct sockaddr_in serverAddr, clientAddr;
    int clientAddrLen = sizeof(clientAddr);
    char buffer[1024] = { 0 };
    const char* message = "Hello from server";

    // 初始化 Winsock
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        std::cerr << "WSAStartup failed." << std::endl;
        return 1;
    }

    // 创建服务器套接字
    if ((serverSocket = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) {
        std::cerr << "Socket creation failed." << std::endl;
        WSACleanup();
        return 1;
    }

    // 设置服务器地址
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = INADDR_ANY;
    serverAddr.sin_port = htons(PORT);

    // 将套接字绑定到服务器地址
    if (bind(serverSocket, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) {
        std::cerr << "Bind failed." << std::endl;
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }

    // 监听连接
    if (listen(serverSocket, 5) == SOCKET_ERROR) {
        std::cerr << "Listen failed." << std::endl;
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }

    std::cout << "Server listening on port " << PORT << std::endl;

    while (true) {
        // 接受客户端连接
        if ((newSocket = accept(serverSocket, (struct sockaddr*)&clientAddr, &clientAddrLen)) == INVALID_SOCKET) {
            std::cerr << "Accept failed." << std::endl;
            closesocket(serverSocket);
            WSACleanup();
            return 1;
        }

        // Convert client IP address to string
        char clientIP[INET_ADDRSTRLEN];
        inet_ntop(AF_INET, &clientAddr.sin_addr, clientIP, INET_ADDRSTRLEN);
        std::cout << "Connection accepted from " << clientIP << ":" << ntohs(clientAddr.sin_port) << std::endl;

        // 从客户端接收消息
        int valread;
        if ((valread = recv(newSocket, buffer, sizeof(buffer), 0)) == SOCKET_ERROR) {
            std::cerr << "Recv failed." << std::endl;
            closesocket(newSocket);
            closesocket(serverSocket);
            WSACleanup();
            return 1;
        }

        if (valread == 0) {
            std::cout << "Client disconnected." << std::endl;
        }
        else {
            std::cout << "Message from client: " << buffer << std::endl;
        }

        // 发送消息到客户端
        if (send(newSocket, message, strlen(message), 0) == SOCKET_ERROR) {
            std::cerr << "Send failed." << std::endl;
            closesocket(newSocket);
            closesocket(serverSocket);
            WSACleanup();
            return 1;
        }

        std::cout << "Message sent to client." << std::endl;

        // 关闭套接字
        closesocket(newSocket);
    }

    // 关闭服务器套接字
    closesocket(serverSocket);
    WSACleanup();

    return 0;
}