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7.6

Sending Broadcast packets using UDP in Linux/C

Asked by mgh_mgharish in User Datagram Protocol (UDP), Linux Networking, Linux Programming

Tags: C, UDP Broadcasting

Hi, here is a code in which we are trying to send a simple broadcast packet to all the computers on the network. But this is not working properly. The sender and receiver programs seem to get struck inside sendto and recvfrom functions respectively.

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SENDER CODE:
____________________
#define PORT 2080
#define DEST_ADDR "255.255.255.255"
 
int main(int argc, char *argv[])
{
	int sockfd;
	int broadcast=1;
	struct sockaddr_in sendaddr;
	struct sockaddr_in recvaddr;
	int numbytes;
	
	if((sockfd = socket(PF_INET,SOCK_DGRAM,0)) == -1)
	{
		perror("sockfd");
		exit(1);
	}
	
	if((setsockopt(sockfd,SOL_SOCKET,SO_BROADCAST,
				&broadcast,sizeof broadcast)) == -1)
	{
		perror("setsockopt - SO_SOCKET ");
		exit(1);
	}
	
   /*if((setsockopt(sockfd,SOL_SOCKET,SO_DONTROUTE,
   			&broadcast,sizeof broadcast)) == -1)
   {
      perror("setsockopt - SO_DONTROUTE");
      exit(1);
   }*/
        	
	sendaddr.sin_family = AF_INET;
	sendaddr.sin_port = PORT;
	sendaddr.sin_addr.s_addr = INADDR_ANY;
	memset(sendaddr.sin_zero,'\0',sizeof sendaddr.sin_zero);
	
	if(bind(sockfd, (struct sockaddr*) &sendaddr, sizeof sendaddr) == -1)
	{
		perror("bind");
		exit(1);
	}
	
	recvaddr.sin_family = AF_INET;
	recvaddr.sin_port = PORT;
	recvaddr.sin_addr.s_addr = inet_addr(DEST_ADDR);
	memset(recvaddr.sin_zero,'\0',sizeof recvaddr.sin_zero);
	
	while((numbytes = sendto(sockfd, "abcd", 4 , 0,
        (struct sockaddr *)&recvaddr, sizeof recvaddr)) != -1) 
   {
   		printf("Sent a packet");
   		sleep(1000);
   }
        perror("sendto");
        exit(1);
   	
	
	close(sockfd);
	
	return 0;
}
____________________
RECEIVER CODE:
____________________
#include "packetize.h"
 
#define PORT 2080
#define DEST_ADDR "10.50.41.208" //Server addr
 
int main(int argc, char *argv[])
{
	int sockfd;
	char buf[10];
	struct hostent *he;
	struct sockaddr_in sendaddr;
	//struct sockaddr_in recvaddr;
	int numbytes;
	int addr_len;
	
	if((sockfd = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
	{
		perror("socket");
		exit(1);
	}
	
	printf("Socket created\n");
	
	if ((he=gethostbyname(DEST_ADDR)) == NULL) 
	{   // get the host info
	   herror("gethostbyname");
   	exit(1);
   }
 
	printf("Host found\n");
 
	sendaddr.sin_family = AF_INET;
	sendaddr.sin_port = PORT;
	sendaddr.sin_addr = *((struct in_addr *)he->h_addr);
	memset(sendaddr.sin_zero,'\0', sizeof sendaddr.sin_zero);
	
	addr_len = sizeof sendaddr;
	if ((numbytes = recvfrom(sockfd, buf, sizeof buf, 0,
              (struct sockaddr *)&sendaddr, (socklen_t *)&addr_len)) == -1) 
	{
   	perror("recvfrom");
      exit(1);
   }
	
	printf("%s",buf);
	
	return 0;
}
____________________
[+][-]01/11/08 01:47 AM, ID: 20635109Expert Comment

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[+][-]01/11/08 03:55 AM, ID: 20635485Author Comment

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[+][-]01/11/08 05:53 AM, ID: 20636182Accepted Solution

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About this solution

Zones: User Datagram Protocol (UDP), Linux Networking, Linux Programming
Tags: C, UDP Broadcasting
Sign Up Now!
Solution Provided By: duncan_roe
Participating Experts: 2
Solution Grade: A
 
[+][-]01/13/08 03:16 AM, ID: 20647301Assisted Solution

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[+][-]01/22/08 08:48 PM, ID: 20720884Expert Comment

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