(Delphi DLL) Cancel HTTP Get Async Task if not Completed after a Max Time

Demonstrates how to wait a maximum amount of time for an asynchronous task to completed. If not completed in the allotted amount of time, the task is cancelled.

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, Task, Http;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
http: HCkHttp;
url: PWideChar;
task: HCkTask;
waitMaxMs: Integer;
wasCanceled: Boolean;
responseStr: PWideChar;

begin
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

http := CkHttp_Create();

// Set some timeouts, in seconds:
CkHttp_putConnectTimeout(http,15);
// ReadTimeout specifies the max number of seconds that must elapse when no additional data is received before
// timing out.  For example, if a server sends a 300 byte response at the rate of 1 byte per second, then
// ReadTimeout would never cause a timeout because there is never a 15 second interval when nothing arrives.
CkHttp_putReadTimeout(http,15);

url := 'https://your-url.com/something';
task := CkHttp_QuickGetStrAsync(http,url);
CkTask_Run(task);

// Wait a maximum of waitMaxMs for the task (i.e. the HTTP GET) to complete.
// The Wait method returns when the task has been canceled, aborted, or completed, or when the max allotted time has passed.
waitMaxMs := 20000;
CkTask_Wait(task,waitMaxMs);

// At this point, the GET may or may not have completed.  
// Rather than checking the Task status, we can call task.Cancel because
// if the Task is no longer running (because it already completed, was canceled or aborted), then the 
// call to Cancel is a NO-OP (meaning it does nothing and the Task's status is unaffected).
// Also, task.Cancel returns True if the task was in the "queued" or "running" state and was canceled or aborted. 
// The method returns False if the task has any other status.
wasCanceled := CkTask_Cancel(task);
if (wasCanceled = True) then
  begin
    Memo1.Lines.Add('The HTTP GET took too long and was canceled.');
  end
else
  begin
    // Find out what happened.
    if (CkTask_getStatusInt(task) = 7) then
      begin
        // The task completed, which means the background thread's call to QuickGetStr completed
        // with success or failure.  Find out which...
        if (CkTask_getTaskSuccess(task) = True) then
          begin
            // Get the string response for the call to QuickGetStr (which happened in Chilkat's background thread).
            responseStr := CkTask__getResultString(task);
            Memo1.Lines.Add(responseStr);
            Memo1.Lines.Add('HTTP GET successful!');
          end
        else
          begin
            Memo1.Lines.Add('HTTP GET failed prior to waitMaxMs...');
            Memo1.Lines.Add(CkTask__resultErrorText(task));
          end;
      end
    else
      begin
        // The task must've been canceled or aborted by some other means..
        Memo1.Lines.Add('Task did not complete.  Final status: ' + CkTask__status(task));
      end;
  end;

CkTask_Dispose(task);

CkHttp_Dispose(http);

end;