dgser_mul.c

Linux 下面多播程序发送接受例子程序

/*
 * datagram multicast server for daytime service 
 */
#include "stdio.h"
#include "errno.h"
#include "signal.h"
#include "netinet/in.h"
#include "netdb.h"
#include "sys/socket.h"

#define DAYTIME      1113 /* port of UDP echo server */
#define MULTICAST_IP "224.0.3.1"
#define INTERFACE    "127.0.0.1"
#define MAXLINE      120

/*this is the same as chapter 8 ,udp server */
void  dg_echo(int sockfd);

int main(int argc, char *argv[])
{
       	int sockfd,maxfdp1; 
      	int n ,socklen;  
        struct sockaddr_in ser_addr,local_addr/*getsockname */;
	struct ip_mreq mreq ;
	
        // const int on=1 ; /* to set SOL_REUSEADDR sockopt on */	
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) { /* Udp */
            perror("socket");
            exit(1);
        }

         if(inet_aton(MULTICAST_IP,&(mreq.imr_multiaddr))<=0){
	  /* IP multicast address of group */
		 perror("inet_aton");
		 exit(1);
	 }
         if(inet_aton(INTERFACE,&(mreq.imr_interface))<0){
	  /* local IP address of interface */
		 perror("inet_aton");
		 exit(1);
	 }
	 /*set sockopt to add the multicast group*/
	 if(setsockopt(sockfd,IPPROTO_IP,IP_ADD_MEMBERSHIP,
				 &(mreq),sizeof(mreq))<0){
		 perror("setsockopt");
		 exit(1);
	 }
	 /*set SOL_REUSEADDR */
	 /*
	 if(setsockopt(sockfd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&on,sizeof(on))<0){
		 perror("setsockopt");
		 exit(1);
		 */

        ser_addr.sin_family = AF_INET;       /* host byte order */
        ser_addr.sin_port = htons(DAYTIME); /* short, network byte order */
        if(inet_aton(MULTICAST_IP,&(ser_addr.sin_addr))<=0){
			perror("inet_aton");
			exit(1);
	}
        bzero(&(ser_addr.sin_zero), 8);     /* zero the rest of the struct */
	if(bind(sockfd,(struct sockaddr*)(&ser_addr),
				sizeof(struct sockaddr))<0){
		perror("bind");
		exit(1);
	}

      	dg_echo(sockfd);

	close(sockfd);
	exit(0);
}

			

void  dg_echo(int sockfd)
{
	struct sockaddr_in cli_addr;
	int size_sock;
        char mesg[MAXLINE];
	socklen_t socklen;
	int n;
	size_sock=sizeof(struct sockaddr);
	for(;;){
		socklen=size_sock;
		n=recvfrom(sockfd,mesg,MAXLINE,0,&cli_addr,&socklen);
		/* this will block for client's coming */
		if(n<0)
		{
			perror("recvfrom");
			exit(1);
		}else if(n==0)
			return ;
		
		if(sendto(sockfd,mesg,n,0,&cli_addr,socklen)<n)
		{
			perror("recvfrom");
			exit(1);
		}
	}
}