I guess you’re lacking some knowledge of Unreal and Arduino. The examples are usually enough XD
Behind the courtains, the plugin works like this: it opens up a Serial Port and let you send and receive bytes through it. That’s the only thing the Serial Port understands: bytes.
So you can use this plugin to talk to anything that uses Serial Port, not just Arduino.
Now, knowing that you can only send and receive bytes, anything you want to do you need to know how to convert that from and to bytes. That’s the basic data unit in binary computers, so anything can be converted to/from bytes.
The protocol thing I told you about is a way for you to know when you are reading the first bytes of a sequence of fixed length. And inside that sequence you’ll have decided exactly which bytes are what.
Imagine a JPEG file, for instance. It have varied sizes, so in order for a JPEG reader software to know when to stop, there must be some bytes in a specific place in the JPEG format (protocol) that tells its size. That’s called the file header.
What you need to do is to define a format for the data you want to exchange with Unreal and, in Unreal, keep searching for the bytes that define the start of the data. When you find it, you’ll know exactly what comes after and how to read it. These first bytes are usually a sequence that should be very unlike to repeat in your data. Like 0xFF 0xFE 0xFD. That specific byte sequence must be a bit hard to find in random data.
The Read/Write Int, Floats and whatnot functions are just methods I left there to ease the conversion of those formats to and from bytes. But the only thing going through the serial port are bytes.