Xojo Plugin

Cancel HTTP Get Async Task if not Completed after a Max Time

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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. Xojo Plugin

Dim success As Boolean
success = False

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

Dim http As New Chilkat.Http

// Set some timeouts, in seconds:
http.ConnectTimeout = 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.
http.ReadTimeout = 15

Dim url As String
url = "https://your-url.com/something"
Dim task As Chilkat.Task
task = http.QuickGetStrAsync(url)
success = task.Run()

// 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.
Dim waitMaxMs As Int32
waitMaxMs = 20000
success = task.Wait(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.
Dim wasCanceled As Boolean
wasCanceled = task.Cancel()
If (wasCanceled = True) Then
    System.DebugLog("The HTTP GET took too long and was canceled.")
Else
    // Find out what happened.
    If (task.StatusInt = 7) Then
        // The task completed, which means the background thread's call to QuickGetStr completed
        // with success or failure.  Find out which...
        If (task.TaskSuccess = True) Then
            // Get the string response for the call to QuickGetStr (which happened in Chilkat's background thread).
            Dim responseStr As String
            responseStr = task.GetResultString()
            System.DebugLog(responseStr)
            System.DebugLog("HTTP GET successful!")
        Else
            System.DebugLog("HTTP GET failed prior to waitMaxMs...")
            System.DebugLog(task.ResultErrorText)
        End If

    Else
        // The task must've been canceled or aborted by some other means..
        System.DebugLog("Task did not complete.  Final status: " + task.Status)
    End If

End If