Multicast Problem - Operation Not Permitted
Hello. I'm attempting to understand network programming in particular Multicasting originally with Python but I hit upon a privilege problem when executing my Python scripts. To try and get round the problem I thought I'd try similar things in C but I still get the same problem i.e. Operation not permitted.
As my learning material I am using the book 'UNIX network programming Volume 1' from Addison Wesley and using code from chapter 21, Multicasting. At first I just simply wanted to send a multicast packet and watch the packets on the network using wireshark. The following is the some code I have taken from the above book, section 21.10 (I have commented out the functions to do with receive:
Code:
#include "unp.h"
void recv_all(int, socklen_t);
void send_all(int, SA *, socklen_t);
int
main(int argc, char **argv)
{
int sendfd, recvfd;
const int on = 1;
socklen_t salen;
struct sockaddr *sasend, *sarecv;
if (argc != 3)
err_quit("usage: sendrecv <IP-multicast-address> <port#>");
sendfd = Udp_client(argv[1], argv[2], (void **) &sasend, &salen);
printf("Send socket is: %i\n",sendfd);
//recvfd = Socket(sasend->sa_family, SOCK_DGRAM, 0);
//Setsockopt(recvfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
//sarecv = Malloc(salen);
//memcpy(sarecv, sasend, salen);
//Bind(recvfd, sarecv, salen);
//Mcast_join(recvfd, sasend, salen, NULL, 0);
//Mcast_set_loop(sendfd, 0);
//if (Fork() == 0)
// recv_all(recvfd, salen); /* child -> receives */
send_all(sendfd, sasend, salen); /* parent -> sends */
}
The code for send_all():
Code:
#include "unp.h"
#include <sys/utsname.h>
#define SENDRATE 5 /* send one datagram every five seconds */
void
send_all(int sendfd, SA *sadest, socklen_t salen)
{
char line[MAXLINE]; /* hostname and process ID */
struct utsname myname;
if (uname(&myname) < 0)
err_sys("uname error");;
snprintf(line, sizeof(line), "%s, %d\n", myname.nodename, getpid());
for ( ; ; ) {
printf("Attempting to send.\n");
Sendto(sendfd, line, strlen(line), 0, sadest, salen);
sleep(SENDRATE);
}
}
The code for Sendto() I cannot find as yet within the book, but I believe it is a wrapper function for the system function sendto().
Unfortunately, when I execute the compiled code I get the following error (even if I use 'sudo' too)
Quote:
sendto error: Operation not permitted
Can anyone tell me how to get permissions to do this as even 'sudo' doesn't work.
(I'm using Ubuntu 10.04)
