cherry.c

用五个实例来解释linux下的c编程

/******* 服务器程序  cherry.c ************/

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

#define WAITBUF 10
#define BUFSIZE 1024

int
main (int argc, char *argv[])
{
  int sockfd, accept_sock;
  struct sockaddr_in server_addr;
  struct sockaddr_in client_addr;
  socklen_t sin_size = sizeof (struct sockaddr_in);
  char reply[] = "I love you too!";
  char buffer[1024] = { 0 };
  int portnumber;
  int nread;

  if (argc != 2)
    {
      fprintf (stderr, "Usage:%s portnumber\a\n", argv[0]);
      exit (1);
    }
  /* 端口号不对，退出 */
  if ((portnumber = atoi (argv[1])) < 0)
    {
      fprintf (stderr, "Usage:%s portnumber\a\n", argv[0]);
      exit (1);
    }

  /* 服务器端开始建立socket描述符 */
  if ((sockfd = socket (AF_INET, SOCK_STREAM, 0)) == -1)
    {
      fprintf (stderr, "Socket error:%s\n\a", strerror (errno));
      exit (1);
    }

  /* 服务器端填充sockaddr结构 */
  bzero (&server_addr, sizeof (struct sockaddr_in));
  server_addr.sin_family = AF_INET;
  /* 自动填充主机IP */
  server_addr.sin_addr.s_addr = htonl (INADDR_ANY);
  server_addr.sin_port = htons (portnumber);

  /* 捆绑sockfd描述符 */
  if (bind
      (sockfd, (struct sockaddr *) (&server_addr),
       sizeof (struct sockaddr)) == -1)
    {
      fprintf (stderr, "Bind error:%s\n\a", strerror (errno));
      exit (1);
    }

  /* 监听sockfd描述符 */
  if (listen (sockfd, WAITBUF) == -1)
    {
      fprintf (stderr, "Listen error:%s\n\a", strerror (errno));
      exit (1);
    }

  /* 服务器阻塞，直到客户程序建立连接 */
  if ((accept_sock =
       accept (sockfd, (struct sockaddr *) (&client_addr), &sin_size)) == -1)
    {
      fprintf (stderr, "Accept error:%s\n\a", strerror (errno));
      exit (1);
    }

  /* 接收并打印客户端发来的数据 */
  if ((nread = recv (accept_sock, buffer, sizeof (buffer), 0)) == -1)
    {
      fprintf (stderr, "recv Error:%s\n", strerror (errno));
      exit (1);
    }
  printf ("%s\n", buffer);
  memset (buffer, 0, sizeof (buffer));

  /* 回复 */
  if (send (accept_sock, reply, strlen (reply), 0) == -1)
    {
      fprintf (stderr, "Send Error:%s\n", strerror (errno));
      exit (1);
    }

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