winsocket2 tcp服务端发送信息到多个tcp客户端

要在Winsock2 TCP服务器中向多个TCP客户端发送信息，可以使用一个循环来迭代每个客户端套接字，并使用send函数向每个客户端发送消息。以下是一个简单的示例代码：

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

#define MAX_CLIENTS 10

int main() {
    WSADATA wsaData;
    SOCKET serverSocket, clientSockets[MAX_CLIENTS];
    struct sockaddr_in serverAddr, clientAddr;
    char ip[INET_ADDRSTRLEN];
    const char* message = "Hello, clients!";
    
    // 初始化Winsock
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        printf("Failed to initialize winsock.\n");
        return 1;
    }
    
    // 创建套接字
    serverSocket = socket(AF_INET, SOCK_STREAM, 0);
    if (serverSocket == INVALID_SOCKET) {
        printf("Failed to create socket.\n");
        WSACleanup();
        return 1;
    }
    
    // 设置服务器地址和端口
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(8080);  // 例如，这里假设服务器监听端口为8080
    serverAddr.sin_addr.s_addr = INADDR_ANY;
    
    // 绑定套接字到服务器地址和端口
    if (bind(serverSocket, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) {
        printf("Failed to bind socket.\n");
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }
    
    // 监听连接
    if (listen(serverSocket, SOMAXCONN) == SOCKET_ERROR) {
        printf("Failed to listen on socket.\n");
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }
    
    printf("Waiting for incoming connections...\n");
    
    // 初始化客户端套接字数组
    for (int i = 0; i < MAX_CLIENTS; ++i) {
        clientSockets[i] = INVALID_SOCKET;
    }
    
    while (1) {
        // 接受客户端连接
        int clientAddrLen = sizeof(clientAddr);
        SOCKET clientSocket = accept(serverSocket, (struct sockaddr*)&clientAddr, &clientAddrLen);
        if (clientSocket == INVALID_SOCKET) {
            printf("Failed to accept client connection.\n");
            closesocket(serverSocket);
            WSACleanup();
            return 1;
        }
        
        // 获取客户端IP地址
        const char* clientIP = inet_ntop(AF_INET, &(clientAddr.sin_addr), ip, INET_ADDRSTRLEN);
        if (clientIP == NULL) {
            printf("Failed to convert IP address to string.\n");
            closesocket(clientSocket);
            closesocket(serverSocket);
            WSACleanup();
            return 1;
        }
        
        printf("Client connected from: %s\n", clientIP);
        
        // 将新的客户端套接字添加到数组中
        for (int i = 0; i < MAX_CLIENTS; ++i) {
            if (clientSockets[i] == INVALID_SOCKET) {
                clientSockets[i] = clientSocket;
                break;
            }
        }
        
        // 向每个客户端发送消息
        for (int i = 0; i < MAX_CLIENTS; ++i) {
            if (clientSockets[i] != INVALID_SOCKET) {
                if (send(clientSockets[i], message, strlen(message), 0) == SOCKET_ERROR) {
                    printf("Failed to send message to client.\n");
                    closesocket(clientSockets[i]);
                    clientSockets[i] = INVALID_SOCKET;
                }
            }
        }
    }
    
    // 关闭套接字和清理Winsock
    for (int i = 0; i < MAX_CLIENTS; ++i) {
        if (clientSockets[i] != INVALID_SOCKET) {
            closesocket(clientSockets[i]);
        }
    }
    closesocket(serverSocket);
    WSACleanup();
    
    return 0;
}

在代码中，服务器创建了一个监听套接字，并等待客户端的连接。一旦有客户端连接成功，accept函数将返回一个新的套接字用于与客户端进行通信。然后，将新的客户端套接字添加到一个数组中，以便在发送消息时能够迭代所有客户端。使用循环遍历数组中的每个客户端套接字，并使用send函数向每个客户端发送指定的消息。请注意，此示例仅适用于TCP套接字连接，并且最多支持10个客户端连接。你可以根据需要调整MAX_CLIENTS的值。