gethostbyname

#include <rtl.h>

HOSTENT *gethostbyname (
    const char *name,  /* Pointer to host name */
    int *err);         /* Pointer to return error code */

The gethostbyname function retrieves host information corresponding to a host name from a host database.

The argument name is a pointer to the null-terminated name of the host to resolve.

The argument err is a pointer to the return error code.

The gethostbyname function is in the RL-TCPnet library. The prototype is defined in rtl.h.

note

• If a negative number is returned, it represents an error code.

The gethostbyname function returns the HOSTENT structure result. On error a NULL is returned.

If err is not NULL, it points to the returned error code:

• SCK_SUCCESS
  The function call is successful.
• SCK_ELOCKED
  The function is locked by another task in RTX environment.
• SCK_EWOULDBLOCK
  The function would block in non blocking mode.
• SCK_EINVALIDPARA
  The function parameter is invalid.
• SCK_ENONAME
  The host name does not exist.
• SCK_ETIMEOUT
  The DNS server did not respond in time.
• SCK_ERROR
  Function failed with generic error code.

getpeername, getsockname

#include <rtl.h>

static const char *hosts[] = {
  "www.google.com",
  "www.keil.com",
  "www.microsoft.com",
  "www.yahoo.com",
  NULL
};

__task void dns_task (void) {
  int i,j,err;
  HOSTENT *host;
  IN_ADDR *addr;

  for (i = 0; ; i++) {
    if (!hosts[i]) i = 0;
    printf ("Host: %s\n",hosts[i]);

    host = gethostbyname (hosts[i], &err);
    if (host == NULL) {
      if (err == SCK_ENONAME) {
        printf ("Hostname does not exist\n");
      }
    }
    else if (host->h_addrtype == AF_INET) {
      for (j = 0; host->h_addr_list[j]; j++) {
        addr = (IN_ADDR *)host->h_addr_list[j];
        printf("IP Address: %d.%d.%d.%d\n",addr->s_b1,
                                           addr->s_b2,
                                           addr->s_b3,
                                           addr->s_b4);
      }
    }
    os_dly_wait (300);
  }
}