test5.c

培训嵌入式linux

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

#define	REMOTE_HOST	"192.168.0.1"
#define	REMOTE_PORT	80

int main(int argc, char **argv)
{
  int fd;

  char *remote_host;
  unsigned short remote_port;
  unsigned long resolved_remote_host;

  if (argc < 3)
  {
    fprintf(stderr, "Usage: %s <target host> <target port>\n", argv[0]);
    exit(1);
  }

  remote_host = argv[1];
  remote_port = atoi(argv[2]);

  //int socket(int domain, int type, int protocol);

/*
  Name Purpose Man page
    PF_UNIX, PF_LOCAL Local communication unix(7)
    PF_INET IPv4 Internet protocols ip(7)
    PF_INET6 IPv6 Internet protocols
    PF_IPX IPX - Novell protocols
    PF_NETLINK Kernel user interface device netlink(7)
    PF_X25 ITU - T X .25 / ISO - 8208 protocol x25(7) PF_AX25 Amateur radio AX .25 protocol PF_ATMPVC Access to raw ATM PVCs PF_APPLETALK Appletalk ddp(7) PF_PACKET Low level packet interface packet(7)
*/

  /*
     SOCK_STREAM
     Provides sequenced, reliable, two - way, connection - based byte streams.An out - of - band data trans -
     mission mechanism may be supported.
     SOCK_DGRAM Supports datagrams(connectionless, unreliable messages of a fixed maximum length).SOCK_SEQPACKET Provides a sequenced, reliable, two - way connection - based data transmission path for datagrams
     of fixed maximum length;
     a consumer is required to read an entire packet with each read system call.
     SOCK_RAW Provides raw network protocol access.SOCK_RDM Provides a reliable datagram layer that does not guarantee ordering.SOCK_PACKET Obsolete and should not be used in new programs;
     see packet(7).
   */

  // XXX: step 1, socket()

  //if ((fd = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
  if ((fd = socket(PF_INET, SOCK_STREAM, 0)) < 0)
  {
    fprintf(stdout, "Create socket by socket() failed: %s\n", strerror(errno));
    return 0;
  }

  fprintf(stdout, "New created socket = %d\n", fd);

  // TODO: step 1.4, DNS resolve

  //struct hostent *gethostbyaddr(const void *addr, socklen_t len,
  //struct hostent *gethostbyname(const char *name);

  struct hostent *h = NULL;

  h = gethostbyname(remote_host);

  if (h == NULL)
  {
    fprintf(stderr, "gethostbyname() failed, h_errno = %d\n", h_errno);

    //The variable h_errno can have the following values:
    switch (h_errno)
    {
      case HOST_NOT_FOUND:
	fprintf(stderr, "The specified host is unknown.\n");
	break;
      case NO_ADDRESS:
	//case NO_DATA:
	fprintf(stderr, "The requested name is valid but does not have an IP address.\n");
	break;
      case NO_RECOVERY:
	fprintf(stderr, "A non-recoverable name server error occurred.\n");
	break;
      case TRY_AGAIN:
	fprintf(stderr, "A temporary error occurred on an authoritative name server.  Try again later.\n");
	break;
    }

    // FIXME: check error code, and deal with it
    exit(1);
  }

  fprintf(stdout, "DNS resolv successed.\n");

#if 0
  struct hostent
  {
    char *h_name;		/* official name of host */
    char **h_aliases;		/* alias list */
    int h_addrtype;		/* host address type */
    int h_length;		/* length of address */
    char **h_addr_list;		/* list of addresses */
  }
#  define h_addr  h_addr_list[0]	/* for backward compatibility */
#endif

  fprintf(stdout, "official name of host: %s\n", h->h_name);

  //fprintf(stdout, "alias list: %s", h->h_name);
  char **pp;

  pp = h->h_aliases;
  while (pp && *pp)
  {
    fprintf(stdout, "\t%s\n", *pp);
    pp++;
  }

  fprintf(stdout, "host address type: %d\n", h->h_addrtype);
  fprintf(stdout, "length of address: %d\n", h->h_length);

  fprintf(stdout, "list of addresses:\n");

  int i = 0;

  pp = h->h_addr_list;
  while (pp && *pp)
  {
    //p = inet_ntoa(*((struct in_addr *) &addr1));
    fprintf(stdout, "\t%p -> %s\n", *pp, inet_ntoa(*(struct in_addr *) *pp));
    //fprintf(stdout, "\t%s\n", inet_ntoa(*(struct in_addr *)*pp));
    pp++;

    if (i == 0)
    {
      resolved_remote_host = *(unsigned long *)*pp;
      i++;
    }
  }

  // XXX: step 1.5 prepare remote server data struct

  // int connect(int sockfd, const struct sockaddr *serv_addr, socklen_t addrlen);
  struct sockaddr_in remote_addr;

  memset(&remote_addr, 0, sizeof(remote_addr));
  remote_addr.sin_family = PF_INET;
  remote_addr.sin_port = htons(remote_port);
  //remote_addr.sin_addr.s_addr = inet_addr(remote_host);
  remote_addr.sin_addr.s_addr = resolved_remote_host;

  // XXX: step 2, connect to remote server
  if (connect(fd, (struct sockaddr *) &remote_addr, sizeof(remote_addr)) < 0)
  {
    fprintf(stdout, "connect to remote host: %s:%d failed: %s\n", remote_host, remote_port, strerror(errno));
    return 0;
  }

  fprintf(stdout, "Connected to remote host: %s:%d\n", remote_host, remote_port);

  // XXX: step 3, send request

  //ssize_t pwrite(int fildes, const void *buf, size_t nbyte, off_t offset);
  //ssize_t write(int fildes, const void *buf, size_t nbyte);
  char buf[1024];

  memset(buf, 0, sizeof(buf));
  strcpy(buf, "GET / HTTP/1.1\n\n");

  // FIXME: check return value fo write()
  if (write(fd, buf, sizeof(buf)) < 0)
  {
    fprintf(stdout, "Send request to %s:%d failed: %s\n", remote_host, remote_port, strerror(errno));
    return 0;
  }

  // XXX: step 4, read response from remote server

  //ssize_t pread(int fildes, void *buf, size_t nbyte, off_t offset);
  //ssize_t read(int fildes, void *buf, size_t nbyte);
  ssize_t n;

  while ((n = read(fd, buf, sizeof(buf))) > 0)
  {
    fprintf(stdout, "%s", buf);
  }

  if (n < 0)
  {
    fprintf(stdout, "Read from %s:%d encounter a error: %s\n", remote_host, remote_port, strerror(errno));
    return 0;
  }
  else if (n == 0)
  {
    fprintf(stdout, "Remote disconnected.\n");
    close(fd);
  }

  // XXX: step 5, disconnect from remote server

  close(fd);

  return 0;
}