Easy way for resolve dns with Indy
lazarus / 38-Networking and Web Programming

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clauslack · 2012-09-18 13:21

Y try a simple function for convert dns name to ip address.

Y try with IdDNSResolver1, but not work

Code: [Select]procedure TForm1.Button1Click(Sender: TObject);
var x:integer;
begin
    with IdDNSResolver1 do begin
        try
            Host := '8.8.8.8';
            QueryType := [qtA];
            Resolve('www.facebook.com',nil,0);
            if QueryResult.Count > 0 then  begin
                  Memo1.Lines.Add(QueryResult.Items[0].name);
                end
                else begin
                Memo1.Lines.Add('no work');
            end;
        finally
            Free;
        end;
    end;
end;                  

Any idea
Thanks

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BeniBela · 2012-09-18 20:55

Why do you want to use Indy for that?

Just fpc alone works like that:

 Code: [Select]uses netdb;
var
  temp: THostEntry;
begin
  ResolveHostByName('google.com', temp);
  writeln(temp.Addr.s_bytes[1],'.',temp.Addr.s_bytes[2],'.',temp.Addr.
s_bytes[3],'.',temp.Addr.s_bytes[4]);
end.

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clauslack · 2012-09-18 21:23

Thanks BeniBela

this works fine.

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BeniBela · 2012-09-19 09:23

Some things you might want to be aware of:

- need another function for ip6 looks up

- on unix, it uses the nameservers from the resolv.conf, it has read
at program start => when the file  later changes it is not
automatically updated => it may fail if the program is started (e.g.
autostart) before an internet connection exists

- there is an option to reload a changed resolv.conf, but then it is
probably not thread safe anymore

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piola · 2023-01-10 15:49

Quote from: BeniBela on September 18, 2012, 10:55:48 pmWhy do you want
to use Indy for that?

Just fpc alone works like that:

 Code: [Select]uses netdb;
var
  temp: THostEntry;
begin
  ResolveHostByName('google.com', temp);
  writeln(temp.Addr.s_bytes[1],'.',temp.Addr.s_bytes[2],'.',temp.Addr.
s_bytes[3],'.',temp.Addr.s_bytes[4]);
end.

I'm sorry for replying to this 10-year-old topic, but it's exactly my
problem. I just want to do a simple DNS lookup and have been googling
quite a lot now. I found dozens of suggestions to use fcl-net and I'd
really like to do so. The example BeniBela has posted is all I want to
do.

Bo no-one has ever mentioned that fcl-net is obviously restricted to
*nix. It doesn't compile on Windows because of the use of BaseUnix in
netdb.pas.

I'd really appreciate a similar example of how to do not more than an
hostname-to-IP-address lookup on Windows 🙈

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MarkMLl · 2023-01-10 16:13

You might be better posting directly into the Windows-specific part of
the forum.

Speaking as somebody who by and large doesn't use Indy etc., I can say
that the fcl-net stuff does still work, and one possibility would be
looking to see what makes it unix-specific: WinSock is actually fairly
close to the de-facto standard Berkeley Sockets stuff... in fact my
notes suggest that the Resolve unit might work with it.

MarkMLl

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loaded · 2023-01-10 17:01

This is how I use it in my applications.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses
resolve,StrUtils; function GetHostByName(HostName:String):String;var 
host:THostResolver;begin  host := THostResolver.Create(nil);  if
host.NameLookup(HostName) then     result := host.AddressAsString 
 else     result := '';  host.Free;end; procedure
TForm1.Button1Click(Sender: TObject);var  host: string;  tip: TStringA
rray;begin Host:='https://google.com/'; Host:=ReplaceStr(ReplaceStr(Re
placeStr(ReplaceStr(ReplaceStr(Host,'https',''),'http',''),'/',''),'\'
,''),':',''); tip:=GetHostByName(Host).Split('.'); showmessage(tip[0]+
'.'+tip[1]+'.'+tip[2]+'.'+tip[3]);end;    
Also, I think you can do it directly with the ping command. But some
more code may be required.

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piola · 2023-01-10 17:11

This is working! Thank you!