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KB80602
Repeated 'Listen for Incoming Communication' on port 502 prevents connection to controller
Revision:  2.0
Published:  9/23/2009
Applies To
Firmware for:
SNAP-PAC-S1
SNAP-PAC-S2
SNAP-PAC-R1
SNAP-PAC-R2
Versions
Problem affects versions:  
R7.0a - R8.4a
Resolution is included beginning in version:  
B8.4b, build date 07/06/2009 and after
Problem is fixed in version:  
R8.5a

SYMPTOMS

PAC Control debug mode and PAC Manager cannot inspect a controller running a strategy that repeatedly calls the Listen for Incoming Communication command on registered TCP port 502. Continually calling this command causes the controller to eventually stop accepting new TCP connection requests on any TCP port.

The correct behavior for a strategy that calls this command on a TCP port which is already configured to listen, is to return an error -440. Instead, the brain returns 0 (success).

CAUSE

Continually calling the Listen for Incoming Communciation command on a port that is already configured to listen, eventually uses up resources that permit a connection. As a result, the brain cannot accept new TCP connection requests on any TCP port.

RESOLUTION

This problem has been fixed. The Listen for Incoming Communication command returns error -440 (instead of 0) when an attempt is made to listen on a port that is already in use. In addtion, the strategy logic should not repeatedly call this command on a port for which error -440 is returned.

Relevant Downloads
No relevant downloads have been specified.
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