lnet HTTP request range
lazarus / 38-Networking and Web Programming

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streeto · 2010-07-02 19:56

Hi. I searched a lot in this forum and have not found a post about
this issue.

I am using lnet TLHTTPClientComponent to download a file. In some
situations, I need to request only a part of the file. In HTTP this
means adding "Range: bytes=start-end" to the header. TLHTTPClient has
the properties RangeStart and RangeEnd, which according to the source
add the proper header to the connection.

The thing is, this does not work. When these properties are set, I get
a OnDisconnect event right after the request. Things work nicely
otherwise. Is this the right way to make a ranged request?

Here is what I use to initialize the connection.

Code: [Select]  Client := TLHTTPClientComponent.Create(nil);
  DecomposeURL(EditUrl.Text, Host, URI, Port);
  Client.Host := Host;
  Client.Port := Port;
  Client.URI := URI;
  Client.Method:= hmGet;
  Client.Timeout := 10000;
  Client.OnDisconnect := @ClientDisconnect;
  Client.OnDoneInput := @ClientDoneInput;
  Client.OnError := @ClientError;
  Client.OnInput := @ClientInput;
  Client.OnProcessHeaders := @ClientProcessHeaders;
  Client.RangeStart := 10;
  Client.RangeEnd := 100;
  Client.SendRequest;

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Almindor · 2010-07-03 13:24

I must admit this area of lNet is outside of my expertise (http was
done by Micha Nelissen [neli]). I'll try to figure out if this is a
bug or something is missing on your end.

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streeto · 2010-07-05 14:04

Just to add some context, and possibly help with the bug report, I
attached a very simple example.

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streeto · 2010-07-08 22:04

Using Synapse it is possible to request a range of a document. One
must work a way around the blocking methods, using threds perhaps.
Here is a sample code:

Code: [Select]  Response := TStringList.Create;
  HTTP := THTTPSend.Create;
  HTTP.RangeStart := 1;
  HTTP.RangeEnd := 300;
  try
    Result := HTTP.HTTPMethod('GET', URL);
    if Result then
      Response.LoadFromStream(HTTP.Document);
  finally
    HTTP.Free;
  end;