写一个完整的c语言socket编程组播初始化收发 数据的例子

在C语言中，通过Socket编程进行组播通信需要使用特定的库，比如`sys/socket.h`, `netinet/in.h`, 和 `arpa/inet.h`。下面是一个简单的例子，展示了如何初始化套接字、加入组播组、发送数据以及接收数据：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define GROUP_IP "224.0.0.1" // 组播地址
#define PORT 12345         // 端口号

// 初始化套接字
int create_socket(void) {
    int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sock == -1) {
        perror("Error creating socket");
        exit(EXIT_FAILURE);
    }
    return sock;
}

// 设置组播选项
void set_multicast(int sock, char *group_ip, unsigned short port) {
    struct ip_mreq mreq;
    struct sockaddr_in addr;

    memset(&mreq, 0, sizeof(mreq));
    mreq.imr_multiaddr.s_addr = inet_addr(group_ip);
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);

    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = htonl(INADDR_ANY); // 广播所有接口

    setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
    if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0) {
        perror("Error setting reuse address");
    }
}

// 发送数据
void send_data(int sock, const char *data, size_t len) {
    struct sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_port = htons(PORT);
    inet_aton(GROUP_IP, &server.sin_addr); // 转换IP地址

    if (sendto(sock, data, len, 0, (struct sockaddr *)&server, sizeof(server)) < 0) {
        perror("Error sending data");
    }
}

// 接收数据
void receive_data(int sock, char *buffer, size_t len) {
    char received[len + 1]; // 加1 for the null terminator
    ssize_t bytes_received;

    bytes_received = recvfrom(sock, received, len, 0, NULL, NULL);
    if (bytes_received > 0) {
        printf("Received %zd bytes: %s\n", bytes_received, received);
    } else if (bytes_received == 0) {
        printf("Connection closed by peer.\n");
    } else {
        perror("Error receiving data");
    }
}

int main() {
    int sock = create_socket();
    set_multicast(sock, GROUP_IP, PORT);

    // 发送示例数据
    const char *message = "Hello from client!";
    send_data(sock, message, strlen(message));

    // 模拟接收数据（这里只是为了演示，实际应用通常会进入无限循环等待接收）
    char buffer[1024];
    receive_data(sock, buffer, sizeof(buffer));

    close(sock);
    return 0;
}

**相关问题--:**
1. 组播是什么在网络通信中的作用？
2. 在实际项目中，如何处理接收组播消息的并发问题？
3. 上述代码中的错误检查部分可以如何进一步完善？