Socket does not respond to broadcasted packets !

ArshDeep · 01-17-2014, 03:09 AM

Hi Team,

I am facing an issue related to UDP sockets on Linux. When a socket is bound to specif IP/Interface address rather than INADDR_ANY, does not send/receive broad casted packets. It can send/receive network packets addressed/destined to that particular IP only, broadcasted packets are discarded. So, broadcasting is totally blocked for such kind of applications/services.

What could be solution to this problem so that while using particular IP be able to listen/send broadcast packets ?

Any quick response is appreciated.

Regards,
Arsh

rtmistler · 01-17-2014, 09:55 AM

Can you show the relevant sections of your code here? Here's an example of socket() and bind() and then you use sendto() and recvfrom(). Are you getting good returns from all your system calls? Try binding to port 0.

Code:

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>

void main(void)
{
    int sd, ret;
    struct sockaddr_in addr;

    sd = socket(AF_INET, SOCK_DGRAM, 0);

    printf("Socket descriptor: %d\n", sd);

    if(sd < 0) {
        printf("Socket call error: %d\n", errno);
        return;
    }

    memset((char *)&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    addr.sin_port = htons(0);

    ret = bind(sd, (struct sockaddr *)&addr, sizeof(addr));

    printf("Return from bind: %d\n", ret);

    if(ret < 0) {
        printf("Bind call error: %d\n", errno);
        return;
    }
}

ArshDeep · 01-21-2014, 11:14 PM

Thanks for your update.
But, please note that I am not using IN_ADDR_ANY in socket.
Please find below code snippet:

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

#define BUFLEN 512
#define PORT 9930

void check(char *s)
{
perror(s);
exit(1);
}

int main(void)
{
struct sockaddr_in si_me, si_other;
int s, i, slen=sizeof(si_other);
char buf[BUFLEN];
char serverIP[50];
int val = 1;

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

if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
check("socket");

setsockopt(s, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));

memset((char *) &si_me, 0, sizeof(si_me));
si_me.sin_family = AF_INET;
si_me.sin_port = htons(PORT);
strcpy(serverIP, "172.26.13.56");
si_me.sin_addr.s_addr = inet_addr(serverIP);
if (bind(s, &si_me, sizeof(si_me))==-1)
check("bind");

while(1)
{
if (recvfrom(s, buf, BUFLEN, 0, &si_other, &slen)==-1)
check("recvfrom()");
printf("Received packet from %s:%d\nData: %s\n\n",
inet_ntoa(si_other.sin_addr), ntohs(si_other.sin_port), buf);
}

close(s);
return 0;
}
-----------

Please let us know if there is any solution to this problem.

rtmistler · 01-22-2014, 09:13 AM

You have to be root and I believe you may have to be INADDR_ANY.