Serial comms to Arduino

General
3

[Edited By Author - reduced code block eliminating code not relevant to OPs question]
Where is Xojo Code that shows the setup of the COM port and serial properties for the COM port you’re trying to use (on the Xojo side)?

For example, I load all the available COM ports on application start into a pop up menu. Once the user selects the desired COM port I initialize it using the code below.

I use Xojo to communicate with the Arduino quite regularly.

''' Make sure a row is selectedin the popup menu, if not, bail out
If popComPorts.SelectedRowIndex = -1 Then
  Return 0
End If

''' Obtain the port id from the row tag of the selected row
Dim port As Integer = Val(popComPorts.RowTagAt(popComPorts.SelectedRowIndex))

''' Set the serial port id and baud rate
SerialConnection1.Device = SerialDevice.At(port)
SerialConnection1.Baud = SerialConnection.Baud57600

''' Try to open the serial port, if success return 1, if not return 0
Try
  SerialConnection1.Connect
  SerialCon = 1 '' Set connection flag
  Return 1
Catch error As IOException
  MessageBox("IOException SerialConnection1.Connect")
  rctCon.FillColor = clrRed
  Return 0
End Try

''' Failed; reset all of the serial port flags and restore window status to not connected
SerialCon = 0
rctCon.FillColor = clrRed
Return 0

Based on your Arduino code, you are not sending anything from Arduino unless you receive something, so I suspect all on Xojo side.