[Lazarus] Accessing freedb.org using Indy's TIdHTTP Get method

[Antonio Fortuny]

Le 10/06/2013 21:49, Alejandro Gonzalo a écrit :
> Using fpc's cddb unit I was able to form the freedb query string from 
> the CD in my drive (for "The Great Bluesmen" it was : 2b10b215 21 150 
> 12557 26267 48645 60997 77047 91730 103462 117580 129470 145975 160670 
> 185985 199220 213447 228725 250610 270005 283037 292752 309990 4276).  
> Using the instructions at
> http://staffwww.dcs.shef.ac.uk/people/D.Abbott/Library/freedb.howto1.06.txt
> I tried using the Get method of Indy's TIdHTTP component to 
> go retrieve the album info, but I just get error messages (usually 500 
> Command syntax error: incorrect number of arguments).
> Could some kind person please give me a successful example of using 
> TIdHttp.get (or the equivalent in Synapse) with freedb.org?  Are there 
> Properties I need to set?
> Thank you.
> A. G.
>
>
I've read in the howto that the GET is not supported and POST bust be 
used instead. After having quickly read the text it seems that the 
request is adressed to a form using fields descriptors. This meand that 
the header must be filled in as the URL requests it. Y guess you shoud 
use something like
var
   data: TIdMultiPartFormDataStream;
   ResponseStream: TStringStream;
   Reponse: String;
   IdIntercept: TIdConnectionIntercept;   // might not be needed

begin
   ... some initialization code

   IdIntercept := TIdConnectionIntercept.Create(nil);   // might not be 
needed
   data := TIdMultiPartFormDataStream.Create;
   with TIdHTTP.Create(nil) do try
      // use a timeout to get control back if URL does not answer
       ConnectTimeout := 20000;

      // might not be needed but usefull to trace what happens
       IdIntercept.OnConnect := @HttpInterceptConnect;
       IdIntercept.OnDisconnect := @HttpInterceptDisconnect;
       IdIntercept.OnReceive := @HttpInterceptReceive;    //  <--- this 
one could be important to use
       IdIntercept.OnSend := @HttpInterceptSend;

       // you maight use these event if you want to inform the use on 
how things are going on
       OnStatus := IdHTTPSStatus;
       OnWork := IdHTTPSWork;
       OnWorkBegin := IdHTTPSWorkBegin;
       OnWorkEnd := IdHTTPSWorkEnd;

       Request.ContentLength := -1;
       Request.ContentRangeEnd := 0;
       Request.ContentRangeStart := 0;
       Request.Accept := 'text/html, */*';
       Request.BasicAuthentication := False;
       Request.UserAgent := 'Some identification(compatible; Indy Library)';
       Request.Username := 'some_uer_if_needed';
       Request.Password := 'user_password?';
       HTTPOptions := [hoForceEncodeParams];
       Request.ContentType := 'application/x-www-form-urlencoded';
       data.AddFormField('no_client', AClient);

       ... as many fields as needed

       Request.ContentLength := data.size;
       ResponseStream.Position := 0;
       Request.ContentLength := data.size;
       Post(HTTPPostServer, data, ResponseStream);
       ResponseStream.Position := 0;
       Reponse := ResponseStream.DataString;

   finally
     Free;
     data.Free;
     IdIntercept .Free
   end

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