Visual FoxPro

Abort a Running SSH Tunnel Operation

Demonstrates the AbortCurrent property, which requests that the currently running foreground operation be aborted. It is intended to be set to true from another thread — for example, to interrupt a synchronous Connect that is waiting for an unresponsive server.

Background: A synchronous call like Connect blocks the calling thread until it finishes or times out, which is a problem when a user clicks "Cancel" or the app needs to shut down. Setting AbortCurrent from a different thread breaks the blocked operation out early, returning a failure the caller can handle. Note its scope is deliberately limited to the current foreground operation: it does not stop the background listener or terminate established tunnel clients — use StopAccepting or CloseTunnel for those.

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LOCAL lnSuccess
LOCAL loTunnel
LOCAL lnSshPort
LOCAL lnWaitForThreadExit

lnSuccess = 0

*  Demonstrates the SshTunnel.AbortCurrent property, which requests that the currently running
*  foreground operation be aborted.

loTunnel = CreateObject('Chilkat.SshTunnel')

*  AbortCurrent is intended to be set to 1 from ANOTHER thread to interrupt a synchronous
*  operation in progress -- for example, a Connect that is waiting for an unresponsive server.
*  It does not stop the background listener or terminate established background tunnel clients.
*  
*  The assignment below illustrates the property.  In a real application it would be set on a
*  separate thread while Connect blocks; if it becomes 1, the blocked Connect returns with a
*  failure.
loTunnel.AbortCurrent = 0

loTunnel.DestHostname = "db.internal.example.com"
loTunnel.DestPort = 5432

lnSshPort = 22
lnSuccess = loTunnel.Connect("ssh.example.com",lnSshPort)
IF (lnSuccess = 0) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    CANCEL
ENDIF

? "Connected."

lnWaitForThreadExit = 1
lnSuccess = loTunnel.CloseTunnel(lnWaitForThreadExit)
IF (lnSuccess = 0) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    CANCEL
ENDIF

RELEASE loTunnel