Unable to read buffer with more than 512 bytes with read function

[aitriago]

Describe the bug
We read and write a JSON config file to a device using read and write functions. If the file is shorter than 512 bytes, everything runs fine. But then it is longer, in Android devices we get up to 512 bytes.

To Reproduce
You will need a device that allows reading/writing capabilities/

1. Scan and connect to the BT using your Android device.
2. Write a string with more than 512 bytes using write function.
3. Read the written string using read function.
4. Compare both strings.

Plugin version:

• @capacitor-community/bluetooth-le: [e.g. 0.4.0]

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Devices where there is no error:

• iPhone (Latest iOS version)
• Samsung S7 with Android Oreo (8.1)

-Devices with the BUG:

• Samsung S23 ultra - Android 14
• Xiaomi Redmi 9 - Android 12
• Samsung Galaxy Tab A8 - Android 14

Additional context
The JSON file we write:

{"wifi": {"ap_pass": "password", "sta_ssid": "Entrepanoles", "sta_pass": "entrepanesq244", "ap_ssid": "tankmont3l3m0"}, "channel": [{"min_level": "10.00", "max_level": "100.00", "chan_label": 1, "type": "RS485|ADC", "name": "Mi tanque grande en el cuarto azul", "min_volt": 0, "idpin": 1, "enable": false, "min_amp": 0, "tank_capacity": "5000.00"}], "info": {"refresh_interval": 30, "model": "XXXXX-S3", "interval": 30, "mcu_id": "3030f959d194", "channels": 1, "url": "https://api.XXXXXXXXX.net/api/v1", "refresh_inerval": 30}}

The JSON file we read:

{"wifi": {"ap_pass": "password", "sta_ssid": "Entrepanoles", "sta_pass": "entrepanesq244", "ap_ssid": "tankmont3l3m0"}, "channel": [{"min_level": "10.00", "max_level": "100.00", "chan_label": 1, "type": "RS485|ADC", "name": "Mi tanque grande en el cuarto azul", "min_volt": 0, "idpin": 1, "enable": false, "min_amp": 0, "tank_capacity": "5000.00"}], "info": {"refresh_interval": 30, "model": "XXXXX-S3", "interval": 30, "mcu_id": "3030f959d194", "channels": 1, "url": "https://api.XXXXXXXXX.net/api/v1", "refresh
Add any other context about the problem here.

[peitschie]

@aitriago this is likely an issue with your Bluetooth device.

Each read command here generally corresponds to a single BLE packet, that normally are usually between 185 up to about 512 bytes. If your payload is exceeding the MTU (maximum transmission unit) that the BLE receiver & BLE device have negotiated, it will be cut off.

You will need to change your peripheral implementation to properly support Long Attribute Reads if you are sending payloads that exceed a single packet. See https://stackoverflow.com/questions/38241986/ble-read-long-characteristics-value-using-android-ios for some discussion about this. But, there's nothing that can be fixed or handled in the plugin for this.

[pwespi]

You will need to change your peripheral implementation to properly support Long Attribute Reads if you are sending payloads that exceed a single packet. See https://stackoverflow.com/questions/38241986/ble-read-long-characteristics-value-using-android-ios for some discussion about this. But, there's nothing that can be fixed or handled in the plugin for this.

I agree. Thank you @peitschie!