(Visual FoxPro) Asynchronous Sockets - Reading/Writing Data

Demonstrates the following using async methods:

Demonstrates receiving text on a socket connection up to and including when an expected CRLF arrives. The example sends an HTTP HEAD request to an HTTP server and then reads the response header using ReceiveToCRLF and ReceiveUntilMatch.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loSocket
LOCAL lnUseTls
LOCAL lnMaxWaitMillisec
LOCAL loConnectTask
LOCAL lnSuccess
LOCAL lnConnectSuccess
LOCAL loSendTask
LOCAL lnSendSuccess
LOCAL loReceiveTask
LOCAL lcResponseStatusLine
LOCAL lcResponseHeaderLine
LOCAL lcRemainderOfHeader

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

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Socket')
loSocket = CreateObject('Chilkat.Socket')

* Connect using TLS to www.chilkatsoft.com
* We could also use a normal TCP connection also by specifying port 80 with useTls = 0.
lnUseTls = 1
lnMaxWaitMillisec = 20000
loConnectTask = loSocket.ConnectAsync("www.chilkatsoft.com",443,lnUseTls,lnMaxWaitMillisec)
IF (loSocket.LastMethodSuccess <> 1) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

* Schedule the task for running on the thread pool.  This changes the task's state
* from Inert to Live.
lnSuccess = loConnectTask.Run()
IF (lnSuccess <> 1) THEN
    ? loConnectTask.LastErrorText
    RELEASE loConnectTask
    RELEASE loSocket
    CANCEL
ENDIF

* The application is now free to do anything else.
* For programming languages where Chilkat supports events, a TaskCompleted
* event will fire when the task is completed.

* For this example, we'll simply sleep and periodically
* check to see when the connection is ready.
DO WHILE loConnectTask.Finished <> 1

    * Sleep 10 ms.
    loConnectTask.SleepMs(10)

ENDDO

* A finished task could be one that was canceled, aborted, or truly finished.  

* If the task was "canceled", it was canceled prior to actually starting.  This could
* happen if the task was canceled while waiting in a thread pool queue to be scheduled by Chilkat's
* background thread pool scheduler.  

* If the task was "aborted", it indicates that it was canceled while running in a background thread.  
* The ResultErrorText will likely indicate that the task was aborted.

* If the task "completed", then it ran to completion, but the actual success/failure of the method
* is determined by the result obtained via a GetResult* method.  (A "completed" task will
* have a StatusInt equal to 7.   If the task finished, but was not completed, then it must've
* been aborted or canceled:
IF (loConnectTask.StatusInt <> 7) THEN
    ? "Task did not complete."
    ? "task status: " + loConnectTask.Status
    RELEASE loConnectTask
    RELEASE loSocket
    CANCEL
ENDIF

lnConnectSuccess = loConnectTask.GetResultBool()
IF (lnConnectSuccess <> 1) THEN
    ? "Connect failed."
    ? loConnectTask.ResultErrorText
    RELEASE loConnectTask
    RELEASE loSocket
    CANCEL
ENDIF

RELEASE loConnectTask

* Tell the socket object that all text is to be sent in the utf-8 encoding,
* and the text received is assumed to be utf-8.
loSocket.StringCharset = "utf-8"

* Send an HTTP HEAD request:
loSendTask = loSocket.SendStringAsync("HEAD / HTTP/1.1" + CHR(13) + CHR(10) + "Host: www.chilkatsoft.com" + CHR(13) + CHR(10) + CHR(13) + CHR(10))
IF (loSocket.LastMethodSuccess <> 1) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

lnSuccess = loSendTask.Run()
IF (lnSuccess <> 1) THEN
    ? loSendTask.LastErrorText
    RELEASE loSendTask
    RELEASE loSocket
    CANCEL
ENDIF

* The application is now free to do anything else.
* For programming languages where Chilkat supports events, 
* a TaskCompleted event will fire when the task is completed.
* This example will simply wait until the task completes...
DO WHILE loSendTask.Finished <> 1
    * Sleep 10 ms.
    loSendTask.SleepMs(10)
ENDDO
IF (loSendTask.StatusInt <> 7) THEN
    ? "Task did not complete."
    ? "task status: " + loSendTask.Status
    RELEASE loSendTask
    RELEASE loSocket
    CANCEL
ENDIF

lnSendSuccess = loSendTask.GetResultBool()
IF (lnSendSuccess <> 1) THEN
    ? "Send failed."
    ? loSendTask.ResultErrorText
    RELEASE loSendTask
    RELEASE loSocket
    CANCEL
ENDIF

RELEASE loSendTask

* Wait a maximum of 4 seconds while no data is forthcoming:
loSocket.MaxReadIdleMs = 4000

* To explain MaxReadIdleMs further:  In Chilkat, a max "idle timeout" is the max time to wait
* while no additional data arrives on the socket.  Imagine if 10MB of data will be received
* where the 1st CRLF occurs at the very end.  As long as the data continues arriving and does not
* halt for more than 4000ms, then the ReceiveToCRLF will continue receiving.  It is only after
* the connection becomes idle for more than 4000ms that the app will giveup and fail the read.

* Get the 1st response line, which should be "HTTP/1.1 200 OK"
loReceiveTask = loSocket.ReceiveToCRLFAsync()
IF (loSocket.LastMethodSuccess <> 1) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

lnSuccess = loReceiveTask.Run()
IF (lnSuccess <> 1) THEN
    ? loReceiveTask.LastErrorText
    RELEASE loReceiveTask
    RELEASE loSocket
    CANCEL
ENDIF

* The application is now free to do anything else.
* For programming languages where Chilkat supports events, 
* a TaskCompleted event will fire when the task is completed.
* This example will simply wait until the task completes...
DO WHILE loReceiveTask.Finished <> 1
    * Sleep 10 ms.
    loReceiveTask.SleepMs(10)
ENDDO
IF (loReceiveTask.StatusInt <> 7) THEN
    ? "Task did not complete."
    ? "task status: " + loReceiveTask.Status
    RELEASE loReceiveTask
    RELEASE loSocket
    CANCEL
ENDIF

lcResponseStatusLine = loReceiveTask.GetResultString()

? "StatusLine: " + lcResponseStatusLine
RELEASE loReceiveTask

* Now get the 1st line of the response header:
lcResponseHeaderLine = loSocket.ReceiveToCRLF()
IF (loSocket.LastMethodSuccess <> 1) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

? "HeaderLine: " + lcResponseHeaderLine

* Now read the remainder of the response header by reading until a double CRLF is seen:
loReceiveTask = loSocket.ReceiveUntilMatchAsync(CHR(13) + CHR(10) + CHR(13) + CHR(10))
IF (loSocket.LastMethodSuccess <> 1) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

lnSuccess = loReceiveTask.Run()
IF (lnSuccess <> 1) THEN
    ? loReceiveTask.LastErrorText
    RELEASE loReceiveTask
    RELEASE loSocket
    CANCEL
ENDIF

* The application is now free to do anything else.
* For programming languages where Chilkat supports events, 
* a TaskCompleted event will fire when the task is completed.
* This example will simply wait until the task completes...
DO WHILE loReceiveTask.Finished <> 1
    * Sleep 10 ms.
    loReceiveTask.SleepMs(10)
ENDDO
IF (loReceiveTask.StatusInt <> 7) THEN
    ? "Task did not complete."
    ? "task status: " + loReceiveTask.Status
    RELEASE loReceiveTask
    RELEASE loSocket
    CANCEL
ENDIF

lcRemainderOfHeader = loReceiveTask.GetResultString()

? "Remainder: " + lcRemainderOfHeader
RELEASE loReceiveTask

* Close the connection with the server
* Wait a max of 20 seconds (20000 millsec)
lnSuccess = loSocket.Close(20000)

RELEASE loSocket