Easy way for resolve dns with Indy

[clauslack]

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

[BeniBela]

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.


[clauslack]

Thanks BeniBela

this works fine.

[BeniBela]

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

[piola]

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.


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 🙈

[MarkMLl]

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

[loaded]

This is how I use it in my applications.

Code: Pascal  [Select][+][-]

1. uses resolve,StrUtils;
2.  
3. function GetHostByName(HostName:String):String;
4. var
5.   host:THostResolver;
6. begin
7.   host := THostResolver.Create(nil);
8.   if host.NameLookup(HostName) then
9.      result := host.AddressAsString
10.    else
11.      result := '';
12.   host.Free;
13. end;
14.  
15. procedure TForm1.Button1Click(Sender: TObject);
16. var
17.   host: string;
18.   tip: TStringArray;
19. begin
20.  Host:='https://google.com/';
21.  Host:=ReplaceStr(ReplaceStr(ReplaceStr(ReplaceStr(ReplaceStr(Host,'https',''),'http',''),'/',''),'\',''),':','');
22.  tip:=GetHostByName(Host).Split('.');
23.  showmessage(tip[0]+'.'+tip[1]+'.'+tip[2]+'.'+tip[3]);
24. end;
25.      

Also, I think you can do it directly with the ping command. But some more code may be required.

[piola]

This is working! Thank you!