Starting DNS

Start the DNS Resolver by calling the function get_host_by_name(). DNS Requests are routed to the DNS Server IP address of an active network interface. If you are using a PPP or SLIP interface and no ethernet interface, you must enable the Use default gateway on remote network option in the configuration.

You must also specify a callback function, which is called from the DNS Client when a DNS event occurs.

static void dns_cbfunc (U8 event, U8 *ip) {
  switch (event) {
    case DNS_EVT_SUCCESS:
      printf("IP Address: %d.%d.%d.%d\n",ip[0],ip[1],ip[2],ip[3]);
      break;
    case DNS_EVT_NONAME:
      printf("Host name does not exist.\n");
      break;
    case DNS_EVT_TIMEOUT:
      printf("DNS Resolver Timeout expired, Host IP not resolved.\n");
      break;
    case DNS_EVT_ERROR:
      printf("DNS Resolver Error, check the host name, labels, etc.\n");
      break;
  }
}

When the required host is found in the local DNS Cache, the callback function is called immediately with the result code DNS_EVT_SUCCESS and provides the IP address of the host to the function. In this case, no actual DNS request packet is sent to the remote DNS Server.

Note

• To use an Embedded DNS Client, you must enable and configure it in the configuration file.
• You can also provide the IP address in a string format to specify the host name. The DNS Client decodes it and returns the decoded IP address to the callback function.