udp.c

STUN（RFC3489）客户端的简单实现

#include <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <linux/sockios.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>

#include "udp.h"

//open a UDP socket,return FILE DESCRIPTOR
int openSocket(void)
{
	int fd;
	
	if((fd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
	{
		fprintf(stderr,"open socket failed:%s\n",strerror(errno));
		exit(1);
	}
	
	return fd;                     
}

//close FILE DESCRIPTOR
void closeSocket(int fd)
{
	close(fd);
}

/*fd for FILE DESCRIPTOR                 */
/*return localhost's IP(local endian)    */
unsigned int getLocalIP(int fd)
{
	struct ifconf conf;
	struct ifreq *ifr;
	char buff[BUFSIZ];
	int num;
	int i;
	int ip;

	conf.ifc_len = BUFSIZ;
	conf.ifc_buf = buff;
	ioctl(fd, SIOCGIFCONF, &conf);
	num = conf.ifc_len / sizeof(struct ifreq);
	ifr = conf.ifc_req;

	for(i=0; i<num; i++)
	{
		struct sockaddr_in *sin = (struct sockaddr_in *)(&ifr->ifr_addr);

		ioctl(fd, SIOCGIFFLAGS, ifr);
		if(((ifr->ifr_flags & IFF_LOOPBACK) == 0) && (ifr->ifr_flags & IFF_UP))
		{
			ip = ntohl(sin->sin_addr.s_addr);
			break;
		}
		ifr++;
	}

	return ip;
}