The first activity is an indication to the port monitor to take some port monitor-specific action. Pressing the Break key to indicate that the line speed should be cycled is an example of a port monitor activity. Not all port monitors need to recognize and respond to the same indications. The indication used to attract the attention of the port monitor is defined by the person who defines the port monitor.
The second activity is an incoming service request. When a service request is received, a port monitor must be able to determine which service is being requested from the port on which the request is received. Note that the same service can be available on more than one port.