It is possible to access the Tftp server via its remote object and interact with its settings and logs. For your needs once you access the remote object you would want to call the GetLogItems method to capture the messages for when a transfer is initiated and completed. This is what we do in the Tftp Server's user interface and in the Workspace Studio.
The caveat is that the api information is not published publicly and is not supported. You will need to spy on the communication between the Tftp service and its user interface to get the details for the hooks.