Extcap - how to use Messages Control Protocol

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I took a deeper look at the python example.

From trial and error using the python example, I was able to figure out that Wireshark will provide control pipes for control operation. The control pipes are provided with command line parameter "--extcap-control-out" and "--extcap-control-in".

These pipes are only provided if the extcap listed a "control" interface during Query For Available Interfaces ("--extcap-interfaces").

For example, responding to --extcap-interfaces with the following: interface {value=COM9}{display=Capture using COM9} control {number=0}{type=selector}{display=Channel}{tooltip=ZigBee Channel}

The presence of "control" interface indicate to "The Extcap Capture Process" to provide --extcap-control-out and --extcap-control-in at capture invocation. So the above example will result in capture started with the following arguments --capture --extcap-interface COM9 --fifo \.\pipe\wireshark_extcap_COM9_20221107203022 --extcap-control-out \.\pipe\wireshark_control_ext_to_ws_COM9_20221107203022 --extcap-control-in \.\pipe\wireshark_control_ws_to_ext_COM9_20221107203022

The named control pipes can then be used by the extcap.

Thanks

Please report back if/when you get this working. :-)
The toolbar and status bar were added in Qt: Add interface toolbar support to support nRF Sniffers extcap interfaces which are written in Python.

None of the Wireshark extcap interface code written in C uses control so if you get a working example that would be great to close the loop that it is doable in C.

An extra paragraph in the WSDG with more info might save someone else heartburn down the road.

Yes it works. I am able to display text in the status bar sent from the extcap.

Both control pipes are opened the same way as the data pipe. That is using CreateFile and ConnectNamedPipe. I spun a thread using _beginthread to handle the control input pipe, similar to the python example mentioned above.

I agree with your comments about an extra paragraph in Wireshark doc would have helped. Thanks for pointing me to the python example.

Cheers!