Xbase++

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 nSuccess
LOCAL oTunnel
LOCAL nSshPort
LOCAL nWaitForThreadExit

nSuccess := 0

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

oTunnel := 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.
oTunnel:AbortCurrent := 0

oTunnel:DestHostname := "db.internal.example.com"
oTunnel:DestPort := 5432

nSshPort := 22
nSuccess := oTunnel:Connect("ssh.example.com", nSshPort)
IF (nSuccess == 0)
    ? oTunnel:LastErrorText
    oTunnel:destroy()
    RETURN
ENDIF

? "Connected."

nWaitForThreadExit := 1
nSuccess := oTunnel:CloseTunnel(nWaitForThreadExit)
IF (nSuccess == 0)
    ? oTunnel:LastErrorText
    oTunnel:destroy()
    RETURN
ENDIF

oTunnel:destroy()