(Delphi DLL) Building a multipart/form-data Request for HTTP Upload

Uploading files to a web server typically requires building a multipart/form-data request where the files are contained in the sub-parts of the MIME request.

Note: HTTP uploads require code on the server-side to receive the upload. For example, see Complete C# ASP.NET HTTP Upload Example

This example produces the following HTTP multipart/form-data request:

POST /something HTTP/1.1
Content-Type: multipart/form-data; boundary=------------070002080409050901090203
Host: domain
Content-Length: 546

--------------070002080409050901090203
Content-Disposition: form-data; name="fileA"; filename="fileA.txt"
Content-Type: text/plain

This is the contents of file A
--------------070002080409050901090203
Content-Disposition: form-data; name="fileB"; filename="fileB.txt"
Content-Type: text/plain

This is the contents of file B
--------------070002080409050901090203
Content-Disposition: form-data; name="fileC"; filename="fileC.txt"
Content-Type: text/plain

This is the contents of file C
--------------070002080409050901090203--

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, HttpRequest;

...

procedure TForm1.Button1Click(Sender: TObject);
var
req: HCkHttpRequest;
requestMime: PWideChar;

begin
// This example demonstrates building a multipart/form-data request.

req := CkHttpRequest_Create();

// The ContentType, HttpVerb, and Path properties should
// always be explicitly set.
CkHttpRequest_putHttpVerb(req,'POST');
CkHttpRequest_putPath(req,'/something');
CkHttpRequest_putContentType(req,'multipart/form-data');

// The contents and name of each file to be uploaded is provided
// by calling any of the following methods:
// AddBytesForUpload
// AddBytesForUpload2
// AddFileForUpload
// AddFileForUpload2
// AddStringForUpload
// AddStringForUpload2

// For this example, we'll provide the contents of the files to be uploaded
// directly as in-memory strings.
CkHttpRequest_AddStringForUpload(req,'fileA','fileA.txt','This is the contents of file A','utf-8');
CkHttpRequest_AddStringForUpload(req,'fileB','fileB.txt','This is the contents of file B','utf-8');
CkHttpRequest_AddStringForUpload(req,'fileC','fileC.txt','This is the contents of file C','utf-8');

// View the request that would be sent if SynchronousRequest was called:
requestMime := CkHttpRequest__generateRequestText(req);
Memo1.Lines.Add(requestMime);

// A few important comments about the HTTP request that is generated:
// 
// 1) Chilkat automatically generates a random boundary string.   In 99.999% of cases, this should 
//    be sufficient.
// 2) The Content-Length header is automatically generated based on the actual length of the MIME message
//    that follows the intial (topmost) MIME header.
// 3) The HOST header will automatically get filled in with the actual domain when SynchronousRequest
//    is called

CkHttpRequest_Dispose(req);

end;