Hi advix,
to send those bytes to a serial port: use the byte array to string function!
First you should make an array of your bytes (0x01, 0xff, 0xff), then use the aforementioned function to get a string from the array. (Byte array and string are just different interpretions of the same data.)
Best regards,
GerdW

using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019