main.cpp

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

#define MAX_LEN 1024 // Maximum message length

int main() {
    int sockfd;
    struct sockaddr_in addr;
    struct ip_mreq mreq;
    char buffer[MAX_LEN + 1];
    int bytes_received;

    // Create a UDP socket
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    memset(&addr, 0, sizeof(addr));

    // Fill in the address structure
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = htonl(INADDR_ANY); // Listen on any interface
    addr.sin_port = htons(12345); // Choose any port number you like

    // Bind the socket to the address
    if (bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    // Specify the multicast group to join
    mreq.imr_multiaddr.s_addr = inet_addr("224.0.0.251"); // Multicast group address
    mreq.imr_interface.s_addr = htonl(INADDR_ANY); // Listen on any interface

    // Join the multicast group
    if (setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&mreq, sizeof(mreq)) < 0) {
        perror("setsockopt");
        exit(EXIT_FAILURE);
    }

    // Receive multicast messages
    while (1) {
        bytes_received = recvfrom(sockfd, buffer, MAX_LEN, 0, NULL, NULL);
        if (bytes_received < 0) {
            perror("recvfrom failed");
            exit(EXIT_FAILURE);
        }
        buffer[bytes_received] = '\0'; // Null-terminate the received data
        printf("Received message: %s\n", buffer);
    }

    // Close the socket
    close(sockfd);

    return 0;
}