[Project source code]

This is the script I use to demonstrate HTTP Range requests through Telnet. Just copy and paste each block of code (including the trailing blank line) into a command window and it will run telnet and make the HTTP request. You can view the test file here. Read HTTP Status Codes (including 418), Methods, Headers, and Access Control (CORS).

telnet delphi.org 80
HEAD /http/httptestfile.txt HTTP/1.1
Host: delphi.org
Connection: close

telnet delphi.org 80
GET /http/httptestfile.txt HTTP/1.1
Host: delphi.org
Connection: close

telnet delphi.org 80
GET /http/httptestfile.txt HTTP/1.1
Host: delphi.org
Range: bytes=0-77
Connection: close

telnet delphi.org 80
GET /http/httptestfile.txt HTTP/1.1
Host: delphi.org
Range: bytes=115-154
Connection: close

telnet delphi.org 80
GET /http/httptestfile.txt HTTP/1.1
Host: delphi.org
Range: bytes=78-113
Connection: close

telnet delphi.org 80
GET /http/httptestfile.txt HTTP/1.1
Host: delphi.org	
Range: bytes=115-154,127-127
Connection: close

This last one stopped working because of a change on the webserver.

Here are the images. They all are available as both JPG and BMP and are 640x472 in resolution.

original.jpg
blue.jpg	green.jpg	red.jpg
purple.jpg	teal.jpg	yellow.jpg

Here is the code I used to stream all 7 images into one image. HTTPClient is a TNetHTTPClient and
HTTPReq is a TNetHTTPRequest on the form. The reason it uses Bitmap images is that they are an uncompressed stream of pixel data, so are easier to recombine into one image.

const
  baseurl: string = 'http://delphi.org/http/';
  files: array[0..5] of string = ('red.bmp','green.bmp','blue.bmp',
    'yellow.bmp','purple.bmp','teal.bmp');

procedure TForm34.Button1Click(Sender: TObject);
var
  resp: IHTTPResponse;
  chunk: Integer;
  mem: TMemoryStream;
  I: Integer;
begin
  resp := HTTPReq.Head(baseurl + 'original.bmp');
  chunk := resp.ContentLength div 12;
  ProgressBar1.Max := resp.ContentLength;
  resp := HTTPReq.Get(baseurl + 'original.bmp');
  mem := TMemoryStream.Create;
  try
    mem.LoadFromStream(resp.ContentStream);
    for I := 5 to 11 do
    begin
      ProgressBar1.Tag := chunk*i;
      if I < 11 then
        httpreq.CustomHeaders['Range'] := 'bytes=' + IntToStr(chunk*i) +'-' + IntToStr(chunk*i+chunk-1)
      else
        httpreq.CustomHeaders['Range'] := 'bytes=' + IntToStr(chunk*i) +'-';
      HTTPReq.MethodString := 'GET';
      button1.Text := files[i mod 6];
      HTTPReq.URL := baseurl + files[i mod 6];
      resp := HTTPReq.Execute();
      mem.Position := chunk*i;
      TMemoryStream(resp.ContentStream).SaveToStream(mem);
    end;
    Image1.Bitmap.LoadFromStream(mem);
  finally
    mem.DisposeOf;
  end;
end;