今天第一次编写了一个建立连接的程序，虽然还不是很懂，是照着书上面copy的，但是调通了也很happy，哈哈。

 客户端的源文件：

#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>

int main (int argc,char * * argv)
{
  int sockfd,numb;
  struct sockaddr_in s;
  struct hostent *host;
  char buf [100];
  int port = 8000;

  if(argc!=2){
    fprintf(stderr,"usage: %s hostname \n",argv [0]);
    exit (1);
}
  if(!(host=gethostbyname (argv[1])))
    {
      perror ("error in resolving hostname");
      exit (1);
}
  sockfd = socket (AF_INET,SOCK_STREAM,0);
  if (sockfd<0){
    perror("socket");
    exit(1);
}
  bzero(&s, sizeof(s));
  s.sin_family=AF_INET;
  s.sin_addr.s_addr=((struct in_addr *)(host -> h_addr)) ->s_addr;
  s.sin_port=htons(port);
  if ((connect(sockfd,(struct sockaddr *) &s,sizeof(s)))!=0){
    perror ("connect");
    exit(1);
  }
  printf ("get connected! \n");
  getchar();
  strcpy(buf,"Give me the first file of the president's office");
  if(send (sockfd,buf,strlen(buf),0)<0){
    perror("send");
    exit(1);
  }
     numb=recv(sockfd,buf,100,0);
     if(numb<0)
{
       perror("recv");
       exit(1);
     }
     buf [numb] ='\0';
     printf("Received= %s \n",buf);
     close(sockfd);
     return 0;

}
服务器端的源文件：

#include<sys/param.h>
#include<stdio.h>
#include<stdlib.h>
#include<errno.h>
#include<string.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<netdb.h>

int port = 8000;
void init_daemon(void)
{
pid_t pid;
int i;
if((pid = fork ()) == -1)
exit(1);
if (pid > 0)
exit(0);
setsid();
for(i=0;i<NOFILE;i++)
close(i);
chdir("/rundir");
umask(0);
return;
}

int main (int ac ,char * * av)
{
 int sockfd,tsockfd;
 int addr_size;
 char buf[100];
 struct sockaddr_in s;
 struct sockaddr_in p;
 char temp_buf[256];

 init_daemon();
 sockfd=socket (AF_INET,SOCK_STREAM,0);
 if (sockfd == -1){
 perror("socker building failure");
 exit (1);
 }
 
 bzero(&s ,sizeof(s));
 s.sin_family = AF_INET;
 s.sin_addr.s_addr = INADDR_ANY;
 s.sin_port = htons(port);

 bzero(&p,sizeof(p));
 p.sin_family =AF_INET;
 p.sin_addr.s_addr = INADDR_ANY;
 p.sin_port = htons(port);
 addr_size = sizeof(p);
 
 if(bind(sockfd,(struct sockaddr *) &s ,sizeof (s))== -1){
 perror("bind");
 exit(1);
 }

 if (listen(sockfd,10) ==-1){
 perror("listen");
 exit(1);
 }

 for(;;){
  tsockfd =accept (sockfd,(struct sockaddr *) &p, &addr_size);
  if ( tsockfd<0 ){
   printf("ft:%d\n",errno);
   perror("accept");
   exit(1);
  }
  if(recv (tsockfd,buf,100,0) < 0){
  perror("recv");
  exit(1);
  }
  strcpy (temp_buf,"Here is the first file of the president's office.");
  if (send(tsockfd,temp_buf,strlen(temp_buf),0<0)){
  perror("send");
  exit(1);
  }
  close(tsockfd);
  printf ("send:%s",temp_buf);
 }
}