AM62A3: The application layer fails to receive UDP broadcast data because the udp port is not monitored

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

#define BROADCAST_IP "239.127.3.1"  // 广播地址
#define PORT 30499                     // 发送到的 UDP 端口
#define MESSAGE "Hello from Ubuntu server"
#define INTERVAL 1                     // 发送间隔（秒）

int main() {
    int sockfd;
    struct sockaddr_in broadcast_addr;
    int broadcast_enable = 1;

    // 创建 UDP 套接字
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("Socket creation failed");
        exit(EXIT_FAILURE);
    }

    // 启用广播选项
    if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast_enable, sizeof(broadcast_enable)) < 0) {
        perror("Error enabling broadcast option");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    // 配置广播地址
    memset(&broadcast_addr, 0, sizeof(broadcast_addr));
    broadcast_addr.sin_family = AF_INET;
    broadcast_addr.sin_addr.s_addr = inet_addr(BROADCAST_IP);  // 使用广播地址
    broadcast_addr.sin_port = htons(PORT);

    printf("Sending UDP broadcast to %s:%d...\n", BROADCAST_IP, PORT);

    // 循环发送广播数据
    while (1) {
        if (sendto(sockfd, MESSAGE, strlen(MESSAGE), 0, (struct sockaddr *)&broadcast_addr, sizeof(broadcast_addr)) < 0) {
            perror("Send failed");
        } else {
            printf("Broadcast message sent: %s\n", MESSAGE);
        }
        sleep(INTERVAL);
    }

    close(sockfd);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

#define PORT 30499           // 接收数据的 UDP 端口
#define BUFFER_SIZE 1024
#define MULTICAST_GROUP "239.127.3.1"  // 多播组地址

int main() {
    int sockfd;
    struct sockaddr_in server_addr;
    char buffer[BUFFER_SIZE];
    ssize_t recv_len;

    // 创建 UDP 套接字
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("Socket creation failed");
        exit(EXIT_FAILURE);
    }
    printf("Socket created successfully.\n");

    /*
	int reuse = 1;
    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (char *)&reuse, sizeof(reuse)) < 0) {
        perror("Setting SO_REUSEADDR failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }
	*/

    // 绑定地址和端口
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);  // 接收所有地址的数据
    server_addr.sin_port = htons(PORT);

    printf("Attempting to bind to port %d...\n", PORT);
    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("Binding failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }
    printf("Successfully bound to port %d.\n", PORT);

    // 加入多播组
    struct ip_mreq mreq;
    mreq.imr_multiaddr.s_addr = inet_addr(MULTICAST_GROUP);  // 多播组地址
    mreq.imr_interface.s_addr = inet_addr(INADDR_ANY);   // 使用本地任意接口
    if (setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
        perror("Adding multicast group failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }
    printf("Joined multicast group %s\n", MULTICAST_GROUP);

    printf("Listening for UDP multicast on port %d...\n", PORT);

    // 循环接收数据
    while (1) {
        struct sockaddr_in client_addr;
        socklen_t addr_len = sizeof(client_addr);
        printf("Waiting to receive data...\n");
        recv_len = recvfrom(sockfd, buffer, BUFFER_SIZE - 1, 0, (struct sockaddr *)&client_addr, &addr_len);

        if (recv_len < 0) {
            perror("Receive failed");
            break;
        } else {
            buffer[recv_len] = '\0';
            printf("Received %zd bytes from %s:%d: %s\n",
                   recv_len, inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), buffer);
        }
    }

    close(sockfd);
    return 0;
}