dgcli_mul.c

Linux 下面多播程序发送接受例子程序

/*
 * datagram multicast client for daytime service 
 * receive all  reply 
 * use SIGALRM to interrup recvfrom 
 * has race condiction problem
 */
#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 MAXLINE  120

void dg_cli(FILE *fp,int sockfd,struct sockaddr_in *pser_addr ,int sock_len) ;
void recv_timeout(int sig_num);

int main(int argc, char *argv[])
{
       	int sockfd; 
      	short  i;  
        struct sockaddr_in ser_addr; /* connector's address information */
	struct in_addr host;
	
        if (argc != 2) {
            fprintf(stderr,"usage: client multicastip\n");
            exit(1);
        }

        if (inet_aton(argv[1],&host)<0) {  /* get the host info */
            perror("inet_ntoa");
	    exit(1);
	}

        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) { /* Udp */
            perror("socket");
            exit(1);
        }

        ser_addr.sin_family = AF_INET;       /* host byte order */
        ser_addr.sin_port = htons(DAYTIME); /* short, network byte order */
	
        ser_addr.sin_addr = host;
        bzero(&(ser_addr.sin_zero), 8);     /* zero the rest of the struct */
	printf("send to %s \n",inet_ntoa(ser_addr.sin_addr));
	dg_cli(stdin,sockfd,&ser_addr,sizeof(ser_addr));
	close(sockfd);
	exit(0);
}

void dg_cli(FILE *fp,int sockfd,struct sockaddr_in *pser_addr ,int socklen) 
{
	char sendline[MAXLINE], recvline[MAXLINE];
	int n ;
	int  len_sock;
	struct sigaction  sig_alrm,save_act;
	struct sockaddr_in *preply_addr=(struct sockaddr_in*)malloc(socklen);
	len_sock=socklen;

	sig_alrm.sa_handler=recv_timeout;
	sigemptyset(&sig_alrm.sa_mask);
	sig_alrm.sa_flags=0;
	sig_alrm.sa_flags&=~SA_RESTART;
	sigaction(SIGALRM,&sig_alrm,&save_act); /* set SIGALRM hander */
	
	
	while(fgets(sendline,MAXLINE,fp)!=NULL){
		if(sendto(sockfd,sendto,strlen(sendline),0,
					(struct sockaddr*)pser_addr,socklen)<0){
			perror("sendto");
			return ;
		}
		alarm(3); /* time out for receive all datagram */
		for(;;){
			n=recvfrom(sockfd,recvline,MAXLINE,
       				MSG_WAITALL,
				(struct sockaddr*)preply_addr,&socklen);
			if(n<0)
			{
				if(errno==EINTR) 
					break;
				perror("read");
				return ;
			}
			else if(n>0)
			{
				recvline[n]='\0';
				printf("%s  recv from %s \n",recvline,
					      inet_ntoa(preply_addr->sin_addr));
				
			}
			
		} /*end of for */
	}/**/
	sigaction(SIGALRM,&save_act,NULL);
	free(preply_addr);
}

void recv_timeout(int sig_num)
{
	return ; /* just generate EINTR */
}