client.c

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <netdb.h>

int main(int argc, char *argv[]) 
{ 
 int sockfd; 
 char buffer[1024]; 
 struct sockaddr_in server_addr; 
 struct hostent *host; 
 int portnumber,nbytes; 

 if(argc!=3) 
 { 
  fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]); 
  exit(1); 
 } 
  
 if((host=gethostbyname(argv[1]))==NULL) 
 { 
        fprintf(stderr,"Gethostname error\n"); 
        exit(1); 
 } 

 if((portnumber=atoi(argv[2]))<0) 
 { 
        fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]); 
        exit(1); 
 } 
  
/* 客户程序开始建立 sockfd描述符  */ 
 if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1) 
 { 
        fprintf(stderr,"Socket Error:%s\a\n",strerror(errno)); 
        exit(1); 
 } 

/* 客户程序填充服务端的资料       */ 
 bzero(&server_addr,sizeof(server_addr)); 
 server_addr.sin_family=AF_INET; 
 server_addr.sin_port=htons(portnumber); 
// server_addr.sin_addr=*((struct in_addr *)host->h_addr_list); 
 server_addr.sin_addr=*((struct in_addr *)host->h_addr);
  
/* 客户程序发起连接请求         */  
 if(connect(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1) 
{ 
  fprintf(stderr,"Connect Error:%s\a\n",strerror(errno)); 
  exit(1); 
} 

/* 连接成功了           */ 
if((nbytes=read(sockfd,buffer,1024))==-1) 
{ 
        fprintf(stderr,"Read Error:%s\n",strerror(errno)); 
        exit(1); 
 } 
 buffer[nbytes]='\0'; 
 printf("I have received:%s\n",buffer); 

/* 结束通讯     */ 
 close(sockfd); 
 
 printf("I have close\n"); 
 exit(0); 
}