Thread: Can't seem to receive UDP packets

I'm trying to get a UDP server working and just can't seem to get it to read in any UDP packets. I can see the packet coming in on the correct interface and port from tcpdump, but my program never logs that it got the data.

I just keep getting a log showing that my recvfrom timed out. I'm pretty sure I'm setting everything up correctly. Anyone have an idea as to what I'm missing?

Code:

int create_listen_socket()
{
	struct sockaddr_in si_me;
	int sock_fd;
	struct ifaddrs * ifAddrStruct=NULL;
	struct ifaddrs * ifa=NULL;
	void * tmpAddrPtr=NULL;
	struct timeval tv;

	memset((char *) &si_me, 0, sizeof(si_me));
	if ((sock_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
	{
		printf("Create socket error %d.\n", errno);
		return -1;
	}

	tv.tv_sec = 5;
	tv.tv_usec = 0;
	if (setsockopt(sock_fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0)
	{
		printf("setsockopt error %d.\n", errno);
		return -1;
	}

	getifaddrs(&ifAddrStruct);
	for (ifa = ifAddrStruct; ifa != NULL; ifa = ifa->ifa_next)
	{
		if ((ifa->ifa_addr->sa_family == AF_INET) &&
				(strcmp(ifa->ifa_name, "eth0") == 0))
		{ // check it is IP4
			// is a valid IP4 Address
			si_me.sin_addr.s_addr = ((struct sockaddr_in *) ifa->ifa_addr)->sin_addr.s_addr;

			tmpAddrPtr=&((struct sockaddr_in *)ifa->ifa_addr)->sin_addr;
			char addressBuffer[INET_ADDRSTRLEN];
			inet_ntop(AF_INET, tmpAddrPtr, addressBuffer, INET_ADDRSTRLEN);
			printf("%s IP Address %s\n", ifa->ifa_name, addressBuffer);
			break;
		}
	}
	if (ifAddrStruct != NULL)
	{
		freeifaddrs(ifAddrStruct);
	}

	si_me.sin_family = AF_INET;
	si_me.sin_port = htons(LISTEN_PORT);
	if (bind(sock_fd, (struct sockaddr*) &si_me, sizeof(si_me)) == -1)
	{
		printf("Bind error %d.\n", errno);
		return -1;
	}

	return sock_fd;
}

void * listen_thread(void * args)
{
	char buf[BUFLEN];
	struct sockaddr_in si_other;
	int slen = sizeof(si_other);
	int num_bytes;
	int sock_fd = create_listen_socket();

	while(sock_fd > 0 &&
			running)
	{
		num_bytes = recvfrom(sock_fd, (void*) buf, BUFLEN, 0, (struct sockaddr*) &si_other, (socklen_t *) &slen);
		if(num_bytes > 0)
		{
			printf("Got data.\n");
		}
		printf("Got %d bytes. errno %d\n", num_bytes, errno);
	}

	return 0;
}

Mods, close this thread if you can. I was running this on a fresh install of CentOS and forgot to turn my firewall off! I didn't realize tcpdump could pick up packets before the firewall.