function GetDomainName(Ip:string):string;
var pH:PHostent;
    data:twsadata;
    ii:dword;
begin
  WSAStartup($101, Data);
  ii:=inet_addr(pchar(ip));
  pH:=gethostbyaddr(@ii,sizeof(ii),PF_INET);
  if (ph<>nil) then
   result:=pH.h_name
  else
   result:='';
  WSACleanup();
end;