如何使用UDP套接字在本地广播消息？

我想在本地向多个应用程序广播消息。 为此，我认为UDP套接字是最好的IPC，如果我错了，请纠正我。

为此，我正在使用以下代码：

用于广播：

/*
** broadcaster.c -- a datagram "client" that can broadcast
*/
#include 
#include 
#include 
#include 
#include 
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include 
#define SERVERPORT 4950    // the port users will be connecting to
int main(int argc, char *argv[])
{
    int sockfd;
    struct sockaddr_in their_addr; // connector's address information
    struct hostent *he;
    int numbytes;
    int broadcast = 1;
    //char broadcast = '1'; // if that doesn't work, try this
    if (argc != 3) {
        fprintf(stderr,"usage: broadcaster hostname message\n");
        exit(1);
    }
    if ((he=gethostbyname(argv[1])) == NULL) {  // get the host info
        perror("gethostbyname");
        exit(1);
    }
    if ((sockfd = socket(AF_UNIX, SOCK_DGRAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }
    // this call is what allows broadcast packets to be sent:
    if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast,
        sizeof broadcast) == -1) {
        perror("setsockopt (SO_BROADCAST)");
        exit(1);
    }
    their_addr.sin_family = AF_UNIX;     // host byte order
    their_addr.sin_port = htons(SERVERPORT); // short, network byte order
    their_addr.sin_addr = *((struct in_addr *)he->h_addr);
    memset(their_addr.sin_zero, '\0', sizeof their_addr.sin_zero);
    if ((numbytes=sendto(sockfd, argv[2], strlen(argv[2]), 0,
             (struct sockaddr *)&their_addr, sizeof their_addr)) == -1) {
        perror("sendto");
        exit(1);
    }
    printf("sent %d bytes to %s\n", numbytes,
        inet_ntoa(their_addr.sin_addr));
    close(sockfd);
    return 0;
}

听取：

/*
** listener.c -- a datagram sockets "server" demo
*/
#include 
#include 
#include 
#include 
#include 
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include 
#define MYPORT "4950"    // the port users will be connecting to
#define MAXBUFLEN 100
// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }
    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
int main(void)
{
    int sockfd;
    struct addrinfo hints, *servinfo, *p;
    int rv;
    int numbytes;
    struct sockaddr_storage their_addr;
    char buf[MAXBUFLEN];
    socklen_t addr_len;
    char s[INET6_ADDRSTRLEN];
    int optval = 1;
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4
    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_flags = AI_PASSIVE; // use my IP
    if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }
    // loop through all the results and bind to the first we can
    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype,
                p->ai_protocol)) == -1) {
            perror("listener: socket");
            continue;
        }
        if(setsockopt(sockfd, SOL_SOCKET,SO_REUSEADDR, &optval, sizeof optval) != 0)
        {
            perror("listener: setsockopt");
            continue;   
        }   
        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            perror("listener: bind");
            continue;
        }
        break;
    }
    if (p == NULL) {
        fprintf(stderr, "listener: failed to bind socket\n");
        return 2;
    }
    freeaddrinfo(servinfo);
    printf("listener: waiting to recvfrom...\n");
    addr_len = sizeof their_addr;
    if ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0,
        (struct sockaddr *)&their_addr, &addr_len)) == -1) {
        perror("recvfrom");
        exit(1);
    }
    printf("listener: got packet from %s\n",
        inet_ntop(their_addr.ss_family,
            get_in_addr((struct sockaddr *)&their_addr),
            s, sizeof s));
    printf("listener: packet is %d bytes long\n", numbytes);
    buf[numbytes] = '\0';
    printf("listener: packet contains \"%s\"\n", buf);
    close(sockfd);
    return 0;
}

问题是我必须像这样传递IP 192.168.1.255，但在实际情况中可能没有eth0接口，只会有环回。 那么我该如何实现这一点？