client.c

linux下使用socket进行网络通信

/* client.c */
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <netinet/in.h>

#define SERVPORT 3333
#define MAXDATASIZE 100

int main(int argc,char *argv[])
{
   int local_sockfd,sendbytes;
   char buf[MAXDATASIZE];
   struct hostent *host;
   /*
      struct hostent {  char *h_name;       //正式主机名
                        char **h_aliases; 	//主机别名
                        int h_addrtype;   	//地址类型
                        int h_length;     	//地址长度
                        char **h_addr_list; //指向IPv4或IPv6的地址指针数组
                     }
   */
   struct sockaddr_in remote_addr;          //connector's address information
   if(argc<2)
   {
      fprintf(stderr,"Please enter the remote's hostname!\n");
      exit(1);	
   }
   if((host=gethostbyname(argv[1]))==NULL)  //gethostbyname将主机名转换为IP地址
   {
      perror("gethostbyname");
      exit(1);	
   }
   if((local_sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
   {
      perror("local socket");
      exit(1);	
   }
   remote_addr.sin_family=AF_INET;
   remote_addr.sin_port=htons(SERVPORT);
   remote_addr.sin_addr=*((struct in_addr *)host->h_addr);   //h_addr是h_addr_list中的第一地址
   bzero(&(remote_addr.sin_zero),8);
   if(connect(local_sockfd,(struct sockaddr *)&remote_addr,sizeof(struct sockaddr))==-1)
   {
      perror("connect");
      exit(1);	
   }
   if((sendbytes=send(local_sockfd,"jaywoo",6,0))==-1)
   {
      perror("send");
      exit(1);	
   }
   close(local_sockfd);
   return 0;
}