tom.c

用五个实例来解释linux下的c编程

/******* 客户端程序  tom.c ************/

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

#define BUFSIZE 1024

int
main (int argc, char *argv[])
{
  int sockfd;
  char buffer[BUFSIZE] = "I love you!";
  struct sockaddr_in server_addr;
  int portnumber, nbytes;

  if (argc != 3)
    {
      fprintf (stderr, "Usage:%s hostname portnumber\a\n", argv[0]);
      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.s_addr = inet_addr (argv[1]);

  /* 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);
    }

  /* 发送“I love you!” */
  if ((nbytes = send (sockfd, buffer, strlen (buffer), 0)) == -1)
    {
      fprintf (stderr, "Send Error:%s\n", strerror (errno));
      exit (1);
    }
  memset (buffer, 0, sizeof (buffer));

  /* 接收回复 */
  if ((nbytes = recv (sockfd, buffer, sizeof (buffer), 0)) == -1)
    {
      fprintf (stderr, "Read Error:%s\n", strerror (errno));
      exit (1);
    }
  buffer[nbytes] = '\0';
  printf ("%s\n", buffer);

  /* 结束通讯 */
  close (sockfd);
  exit (0);
}