How to broadcast a message with EddyStone beacon?

Question

I am using a pi as a beacon and I have implemented EddyStone beacon URL. I can broadcast short URLs with no issue but now I want to broadcast a simple message which is stored as a string in a text file.

I would like to read the text file and broadcast it when the beacon is on. Can anyone help me with this? thanks in advance. Here's my code:

import os

on_bluetooth = os.system("sudo hciconfig hci0 up")   # bluetooth on
discoverable_on = os.system("sudo hciconfig hci0 leadv 3")   # discoverable on but not connectable

cond = True
while cond:
    try:
        fh = open('/home/Desktop/message.txt')
        cond = False
    
    except:
        print('File does not exist.')
        continue
    
    for line in fh:
        line = line.rstrip()
        text = line
    
    print("The message is:", text)

message = os.system("sudo hcitool -i hci0 cmd 0x08 0x0008 <insert text variable here>")   # broadcast message

Answer 1

I find Jos Ryke's Beacon Cheat Sheet that he posted on Twitter very helpful to understand what is going on:

https://twitter.com/josryke/status/763006284052463617

As you will see there is only a maximum of 18 bytes for the URL. Even with the bit of encoding they do in the Eddystone format, it is still not a very long url. A common way to get around this is to use a url shortener.

As a side note, hciconfig and hcitools are part of the list of tools that have been deprecated by the BlueZ project

To do a beacon on the command line you can use either bluetoothctl:

(venv) pi@raspberrypi:~ $ bluetoothctl 
Agent registered
[bluetooth]# menu advertise 
[bluetooth]# uuids feaa
[bluetooth]# service 0xfeaa 0x10 0x00 0x00 0x62 0x6c 0x75 0x65 0x74 0x6f 0x6f 0x74 0x68 0x00
[bluetooth]# back
[bluetooth]# advertise on
[CHG] Controller B8:27:EB:22:57:E0 SupportedInstances: 0x04
[CHG] Controller B8:27:EB:22:57:E0 ActiveInstances: 0x01
Advertising object registered
UUID: (feaa)
UUID: Google(0xfeaa)
  10 00 00 62 6c 75 65 74 6f 6f 74 68 00           ...bluetooth.   
Tx Power: off
Name: off
Appearance: off
Discoverable: off
[bluetooth]# 

Or btmgmt:

pi@raspberrypi:~ $ sudo btmgmt add-adv -u feaa -d 1016aafe100001626c7565746f6f746800 -g 1

As you are doing this in a Python script, there is an API available to do it without system calls.

There is a question that already covers this: https://stackoverflow.com/questions/63625654/how-to-create-eddystone-beacon-using-bluez-and-python/63627007#63627007

They do it modifying the TestAdvertisement class in the example advertisement in the BlueZ source code: https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/test/example-advertisement