广播与多播编程

广播服务器端：

/*
 * =====================================================================================
 *
 *       Filename:  tserv.c
 *
 *    Description:  
 *
 *        Version:  1.0
 *        Created:  2012年02月23日 15时15分57秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  MaZheng (blog.youkuaiyun.com/mazheng1989), mazheng19891019@gmail.com
 *        Company:  Dalian University Of Technology
 *
 * =====================================================================================
 */


#include	<stdio.h>
#include	<unistd.h>
#include	<sys/socket.h>
#include	<arpa/inet.h>
#include	<sys/ioctl.h>
#include	<string.h>
#include	<time.h>
#define	BUFLEN 255			/*  */
void getcurtime(char *curtime)
{
	time_t tm;
	time(&tm);
	/*在curtime中放入当前时间的asc表示*/
	snprintf(curtime,BUFLEN,"%s\n",ctime(&tm));
}
int main(int argc,char **argv)
{
	struct sockaddr_in peeraddr;
	int sockfd,on=1;
	char msg[BUFLEN+1];
	if(argc!=3)
	{
		printf("usage:%s<ip address><port>\n",argv[0]);
		exit(0);
	}
	sockfd=socket(AF_INET,SOCK_DGRAM,0);
	if(sockfd<0)
	{
		fprintf(stderr,"socket creating error in tserv.c\n");
		exit(1);
	}
	setsockopt(sockfd,SOL_SOCKET,SO_BROADCAST,&on,sizeof(int));/*设置广播方式*/
	memset(&peeraddr,0,sizeof(struct sockaddr_in));
	peeraddr.sin_family=AF_INET;
	if(inet_pton(AF_INET,argv[1],&peeraddr.sin_addr)<=0)
	{
		printf("Wrong dest IP address\n");
		exit(0);
	}
	int temp;
	sscanf(argv[2],"%d",&temp);
	peeraddr.sin_port=htons(temp);
	for(;;)
	{
		getcurtime(msg);
		int a;
		a=sendto(sockfd,msg,strlen(msg),0,(struct sockaddr *)&peeraddr,sizeof(struct sockaddr_in));
		printf("%d\n",a);
		fflush(stdout);
		sleep(10);
	}
	return 0;
}

运行命令：$:gcc tserv.c -o tserv

                 $:./tserv  222.26.218.255 1234  (222.26.218.255为本地inet广播地址，查看方法为命令为：$:ifconfig )

广播客户端：

/*
 * =====================================================================================
 *
 *       Filename:  tcli.c
 *
 *    Description:  
 *
 *        Version:  1.0
 *        Created:  2012年02月23日 15时38分26秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  MaZheng (blog.youkuaiyun.com/mazheng1989), mazheng19891019@gmail.com
 *        Company:  Dalian University Of Technology
 *
 * =====================================================================================
 */


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

#define	BUFLEN 255			/*  */
int main(int argc,char **argv)
{
	struct sockaddr_in localaddr;
	int sockfd,n;
	char msg[BUFLEN+1];
	if(argc!=2)
	{
		printf("usage:%s <port>\n",argv[0]);
		exit(0);
	}
	sockfd=socket(AF_INET,SOCK_DGRAM,0);
	if(sockfd<0)
	{
		fprintf(stderr,"socket creating error in tcli.c\n");
		exit(1);
	}
	memset(&localaddr,0,sizeof(struct sockaddr_in));
	int temp;
	sscanf(argv[1],"%d",&temp);
	localaddr.sin_port=htons(temp);
	localaddr.sin_addr.s_addr=htonl(INADDR_ANY);
	int opt=SO_REUSEADDR;
	setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt));
	if(bind(sockfd,(struct sockaddr*)&localaddr,sizeof(struct sockaddr_in))<0)
	{
		fprintf(stderr,"bind error in tcli.c\n");
		exit(2);
	}
	n=read(sockfd,msg,BUFLEN);
	if(n==-1)
	{
		fprintf(stderr,"read error in tcli.c\n");
		exit(3);
	}
	else
	{
		msg[n]=0;
		printf("%s",msg);
	}
	return 0;
}