windows 写一个tcp的服务端

以下是一个简单的 TCP 服务端的示例代码，用于接收客户端的连接并向客户端发送消息。

#include <stdio.h>
#include <winsock2.h>

#pragma comment(lib, "ws2_32.lib")

int main() {
    WSADATA wsaData;
    SOCKET listenSocket, clientSocket;
    struct sockaddr_in serverAddr, clientAddr;
    int clientAddrLen = sizeof(clientAddr);
    int ret;

    // 初始化 Winsock
    ret = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (ret != 0) {
        printf("WSAStartup() failed with error: %d\n", ret);
        return 1;
    }

    // 创建监听 socket
    listenSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (listenSocket == INVALID_SOCKET) {
        printf("socket() failed with error: %ld\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }

    // 绑定监听 socket 到本地 IP 地址和端口
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    serverAddr.sin_port = htons(12345);
    ret = bind(listenSocket, (struct sockaddr*)&serverAddr, sizeof(serverAddr));
    if (ret != 0) {
        printf("bind() failed with error: %d\n", WSAGetLastError());
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    // 开始监听客户端连接
    ret = listen(listenSocket, SOMAXCONN);
    if (ret != 0) {
        printf("listen() failed with error: %d\n", WSAGetLastError());
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    printf("Server is listening on port %d\n", ntohs(serverAddr.sin_port));

    // 接受客户端连接并发送消息
    clientSocket = accept(listenSocket, (struct sockaddr*)&clientAddr, &clientAddrLen);
    if (clientSocket == INVALID_SOCKET) {
        printf("accept() failed with error: %d\n", WSAGetLastError());
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    printf("Client connected from %s:%d\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port));

    const char* message = "Hello, client!\n";
    send(clientSocket, message, strlen(message), 0);

    // 关闭 socket
    closesocket(clientSocket);
    closesocket(listenSocket);

    // 清理 Winsock
    WSACleanup();

    return 0;
}

需要注意的是，此代码只适用于 Windows 系统，并且需要链接 `ws2_32.lib` 库。另外，本示例代码省略了错误处理和异常情况的处理，实际应用中需要根据具体情况进行适当的处理。