multicast on all network interface (only linux

multicast.cpp

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

bool multicast( const char* ip, unsigned short port, const char* data, size_t size, int ttl, bool loopback ) {
    struct sockaddr_in groupaddr;
    struct in_addr localinterface;

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

    groupaddr.sin_family = AF_INET;
    groupaddr.sin_addr.s_addr = inet_addr(ip);
    groupaddr.sin_port = htons(port);


    struct ifaddrs *addrs = 0;
    if( getifaddrs( &addrs ) ) {
        return false;
    }
    if ( !addrs )
        return false;

    struct ifaddrs* temp = addrs;//for freeifaddrs

    unsigned long loaddr = inet_addr("127.0.0.1");

    bool bOK = false;
    while( addrs != 0 ) {
        struct sockaddr* soaddr = addrs->ifa_addr;
        const char* ifname = addrs->ifa_name;
        addrs = addrs->ifa_next;
        if(!soaddr || soaddr->sa_family != AF_INET )
            continue;

        if( ((struct sockaddr_in*)soaddr)->sin_addr.s_addr == loaddr )
            continue;

        //printf("broadcast on %s\n", ifname);

        int sock = socket( AF_INET, SOCK_DGRAM, 0 );
        if( !sock )
            return false;

        localinterface.s_addr = ((struct sockaddr_in*)soaddr)->sin_addr.s_addr;

        if(setsockopt(sock, IPPROTO_IP, IP_MULTICAST_IF, (char *)&localinterface, sizeof(localinterface)) < 0) {
            close(sock);
            continue;
        }

        char loop = loopback ? 1 : 0;
        if( setsockopt( sock, IPPROTO_IP, IP_MULTICAST_LOOP, (char *)&loop, sizeof(loop)) < 0 ) {
            close(sock);
            continue;
        }

        if( sendto( sock, data, size, 0 , (struct sockaddr*)&groupaddr, sizeof(groupaddr) ) == size ) {
            bOK = true;
        }
        close(sock);
    };

    freeifaddrs(temp);

    return bOK;
}