Merge pull request #756 from JAndrassy/sockethlp_dnsipn

SocketHelpers - added dnsIP(n) getter as in WiFi libraries

Author: facchinm

libraries/SocketWrapper/src/SocketHelpers.cpp

@@ -50,6 +50,13 @@ arduino::IPAddress arduino::MbedSocketClass::dnsServerIP() {
   return ipAddressFromSocketAddress(ip);
 }
 
+arduino::IPAddress arduino::MbedSocketClass::dnsIP(int n) {
+  SocketAddress ip;
+  NetworkInterface* interface = getNetwork();
+  interface->get_dns_server(n, &ip, nullptr);
+  return ipAddressFromSocketAddress(ip);
+}
+
 void arduino::MbedSocketClass::config(arduino::IPAddress local_ip) {
   nsapi_addr_t convertedIP = { NSAPI_IPv4, { local_ip[0], local_ip[1], local_ip[2], local_ip[3] } };
   _ip = SocketAddress(convertedIP);

libraries/SocketWrapper/src/SocketHelpers.h

@@ -99,6 +99,13 @@ class MbedSocketClass {
      */
   IPAddress dnsServerIP();
 
+  /*
+     * Get the DNS Server ip address.
+     *
+     * return: DNS Server ip address value
+     */
+  IPAddress dnsIP(int n = 0);
+
   virtual NetworkInterface* getNetwork() = 0;
 
   int download(char* url, const char* target, bool const is_https = false);