pctalk.c

一个在linux环境下运行的ＵＤＰ应用程序

#include	<stdio.h>
#include	<stdlib.h>
#include	<unistd.h>
#include	<errno.h>
#include	<string.h>
#include	<sys/types.h>
#include	<sys/socket.h>
#include	<netinet/in.h>
#include	<arpa/inet.h>
#include	<netdb.h>
#define MYPORT	4950

//#define	MAXBUFLEN	100
int	main(int argc,	char * argv[])
{
	int sockfd,numbytes;
	struct	sockaddr_in	server_addr;
	struct	sockaddr_in	clients_addr;
	struct	hostent	*he;
	char	send_buf[256],recv_buf[256];

	if(argc != 2)
	{
		fprintf(stderr,"usage: talker hostname\n");
		exit(1);	
	}
	
	if((he=gethostbyname(argv[1]))==NULL)
	{
		perror("gethostbyname");
		exit(1);
	}
	
	if((sockfd=socket(AF_INET,SOCK_DGRAM,0))==-1)
	{
		perror("socket");
		exit(1);
	}
	server_addr.sin_family=AF_INET;
	server_addr.sin_port =htons(MYPORT);
	server_addr.sin_addr.s_addr=INADDR_ANY;
	memset(&(server_addr.sin_zero),'\0',8);
	if(bind(sockfd,(struct sockaddr *)&server_addr,sizeof(struct sockaddr))==-1)
	{
		perror("bind");
		exit(1);
	}
	while(1)
	{
		char	*ptr;
		int addr_len;
		addr_len=sizeof(struct sockaddr);
		clients_addr.sin_family=AF_INET;	
		clients_addr.sin_port=htons(MYPORT);
		clients_addr.sin_addr=*((struct in_addr *)he->h_addr);
		memset(&(clients_addr.sin_zero),'\0',8);
             //pc first talk
		printf("pc says:");
		ptr=send_buf;
	
		do
		{
			*ptr=getchar();
			ptr++;
		}while(*(ptr-1)!='\n');
		*ptr=0;
		if((numbytes=sendto(sockfd,send_buf,strlen(send_buf),0,(struct sockaddr *)&clients_addr,sizeof(struct sockaddr)))==-1)
		{
		perror("sendto");
		exit(1);
		} 
		if((numbytes=recvfrom(sockfd,recv_buf,255,0,(struct sockaddr *)&clients_addr,&addr_len))==-1)
		{
		perror("recvfrom");
		exit(1);
		}
		recv_buf[numbytes]='\0';
		printf("%s says:%s \n",inet_ntoa(clients_addr.sin_addr),recv_buf);
	}
	close(sockfd);
	return 0;
}