Turning on the Tap

The ability to act as a tap is provided by a special version of the LayGO stack DLL or shared object. The special version is provided in the DLM distribution in the lib/<platform> directory, where <platform> is one of win32, linux or solaris. The tap enabled library should be installed in place of the standard library from the LayGO distribution.

Tapping inside the LayGO stack is enabled on a line-by-line basis using the tap mode parameter in the X.21 bis layer configuration profile. The default mode is disabled. Currently, the only other supported mode is enabled:

Tap mode <0=Disabled 1=Enabled> (0):

For details on creating and editing configuration profiles, see the LayGO Configuration Manual.

Each X.21 bis device checks this parameter when it is opened. If tapping is enabled, it tries to connect to the DLM server running on localhost. If the server is not running on the same host as the tap, the environment variable DLMHOST should be set to show the name or IP address of the host the server is running on.

By default, the tap attempts to connect to the server on TCP port 2713. If the server has been configured to listen on another port, set the environment variable DLMPORT on the tap host to the server's port number.

By default, the tap sends the entire contents of every frame to the server. If less data is required, set the environment variable DLMLIMIT on the tap host to the maximum number of bytes from each frame which should be forwarded.