2.c

linux下面进行网络编程的几个小实例

#include <stdio.h>  
#include <stdlib.h> 
#include <errno.h>  
#include <string.h>  
#include <netdb.h>  
#include <sys/types.h>  
#include <netinet/in.h>  
#include <sys/socket.h>  
#define PORT 3490  
#define MAXDATASIZE 100 /*每次最大数据传输量 */  
int main(int argc, char *argv[])  
{  
int sockfd, numbytes;  
char buf[MAXDATASIZE];  
struct hostent *he;  
struct sockaddr_in their_addr;  
if (argc != 2) {  
  fprintf(stderr,"usage: client hostname"); 
exit(1); 
}  
if((he=gethostbyname(argv[1]))==NULL) {  
  herror("gethostbyname"); 
exit(1);
 }  
if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {  
  perror("socket"); 
exit(1); 
}  
their_addr.sin_family=AF_INET;  
their_addr.sin_port=htons(PORT);  
their_addr.sin_addr = *((struct in_addr *)he->h_addr);  
bzero(&(their_addr.sin_zero),8);  
if (connect(sockfd, (struct sockaddr *)&their_addr,  sizeof(struct sockaddr)) == -1) {/*错误检测*/  
   　　perror("connect"); 
exit(1); 
}  
if ((numbytes=recv(sockfd, buf, MAXDATASIZE, 0)) == -1) {  
   perror("recv"); 
exit(1); 
}  
buf[numbytes] = '';  
printf("Received: %s",buf);  
close(sockfd);  
return 0;  
}