$protocol = 'tcp'
This function returns the service associated with port for the specified protocol as per '/etc/services'.
integer $port - port to check
string $protocol -
name of service running on the port
This function can be called statically.
The name of the service is retrieved from the machine where Net_Portscan is executed, not from the remote host, which you possibly used in Net_Portscan::checkPort().