Message Syntax for File, Smart Card, and Bluetooth Devices

Last modified: November 4, 2025

Introduction

To enable Mendix Workstation Client to communicate with your devices, you must ensure that the messages you send have the correct syntax. This syntax varies depending on the type of device. The following sections show the required syntax for file system, smart card, and Bluetooth devices.

Bluetooth

This device type requires the following message and response:

Message

  • 0#ServiceUUID#CharacteristicUUID - Subscribe to characteristic CharacteristicUUID from service ServiceUUID.
  • 1#ServiceUUID#CharacteristicUUID - Unsubscribe from characteristic CharacteristicUUID from service ServiceUUID.
  • 2#ServiceUUID#CharacteristicUUID - Read characteristic CharacteristicUUID from service ServiceUUID.
  • 3#ServiceUUID#CharacteristicUUID - Write to characteristic CharacteristicUUID from service ServiceUUID.

Response

  • CharacteristicUUID#Response

File System

This device type requires the following message and response:  

Message

  • 0#Directory - Watch for changes in Directory. If Directory is a file path, then watch for changes in the file. Directory is relative to the folder configured in Workspace management. Environment variables (for example, %public%) are supported.
  • 1#Directory - Stop watching for changes in Directory.  
  • 2#File path - Read file at File path.
  • 3#File path#Data#flag - Write to file at File path. The flag can be w for overwrite, a for append If left blank, the value defaults to w.

Response

  • R#File name - File name was renamed (also triggered when file is created and deleted)
  • C#File name - File name was changed
  • D#Data - Data from file read
  • E#Error - Error message from operating system
  • S#{0,1,2,3}#directory - The command {0,1,2,3} on directory was successful.

Example Test

The section below shows a sample test that you can run to verify the configuration.

  1. Create a new Workspace in the Workstation Management.

  2. Create a new Station.

  3. Add a File Device with the following configuration to this Station:

    • Device Name - Write files to test folder
    • Allowed Folder - For example, on a Windows computer you can use a path like C:\MyTestFolder
    • Allow writing files - Yes
    • Use the default values for everything else

  4. Register the Station to your computer (assuming the Workstation Client is installed there).

  5. In your Workspace, navigate to Test Your Station and click on the configured file device.

  6. Enter 3#test.txt#Hello from Mendix in the Send Message field, and then press Send Message.

    The test should show a response like S#3#C:\MyTestFolder\test.txt to indicate that the text file test.txt was succesfully written to MyTestFolder.

  7. Go to C:\MyTestFolder and verify that it contains the text file.

  8. Open the test file and verify that it contains the text Hello from Mendix.

Smart Cards

This device type requires the following message and response:

Message

Send instruction in hexadecimal as a string, for example, FFCA000000. The messages exchanged with the smart card are APDU messages. For more information, refer to the documentation of the APDU command for your smart card reader.

Response

  • 0# - Card connected
  • 1# - Card disconnected
  • 2# Response - Response from device as raw hexadecimal.
  • 3# Error - Error message from device.