uses WinSock;

function TForm_Main.GetIPName(IP: String): String;
var
  WSAData: TWSAData;
  sin: TSockAddrIn;
  pHost: PHostEnt;
begin
  WSAStartup($0202, WSAData);

  sin.sin_family := AF_INET;

  sin.sin_addr.S_addr := Inet_Addr(pChar(IP));

  pHost := gethostbyaddr(Pointer(@sin.sin_addr), 4, PF_INET);

  if pHost <> nil then
  begin
    Result := pHost^.h_name;
  end
  else
  begin
    Result := '';
  end;

  WSACleanup;

end;