First of all try to find your device in the list of supported devices. Third column of the corresponding row contains default port number for your device. Note that sometimes it does not work (usually for cheapest no-name devices) because different manufacturers re-use same popular name (e.g. TK103) for their own devices.
If given port does not work for your device or you cannot find your device in the list of supported devices follow steps below.
If you were not able to find match in the file you can go through all unit tests and try to find match there.
This instruction does not work for binary protocols.