BLE communication between two Raspberry Pi 4 - python-3.x

Question

I am collecting pressure sensor data from 4 Arduino Nano 33 ble to a raspberry pi 4. I am able to receive the data from all the sensors. Now, I want to send this received data to another Raspberry Pi 4 using BLE communication in real-time such that the first Raspberry Pi acts as a repeater. I searched but could not find a suitable approach or solution to implement this.
The first Raspberry Pi could act as a peripheral/client sending all the received sensor data and the second raspberry pi could act as a central/server to receive all the sensor data which can be further displayed on web interfaces or stored in a database.
I tried connecting initially with one Arduino and sending its data over raspberry Pi. I have written the code for Raspberry Pi Client and Server using Bluedot library in Python.
Raspberry Pi 4 Client code
import sys
import time
from bluepy import btle
from bluedot.btcomm import BluetoothClient
from signal import pause
def data_3():
mac_adrs3 = 'f3:9a:9a:e8:54:5c'
print("Connecting..")
tp3_sense = btle.Peripheral(mac_adrs3)
print("Discovering Services..")
_=tp3_sense.services
tire3_sensing_service = tp3_sense.getServiceByUUID("2b7537ab-8899-4359-a78a-096e076a4605")
print("Discovering characteristics..")
_= tire3_sensing_service.getCharacteristics()
return tire3_sensing_service
def byte_array_to_int(value):
value = bytearray(value)
value = int.from_bytes(value, byteorder='little')
return value
def byte_array_to_char(value):
value = value.decode("utf-8")
return value
def decimal_exponent_two(value):
return value/100
def decimal_exponent_one(value):
return value/10
def pascals_to_kilopascals(value):
return value / 1000
def read_pressure3(service3):
pres3_char = service3.getCharacteristics("9c30d6b2-e3d3-4eae-8641-425a36d550ec")[0]
pres3 = pres3_char.read()
pres3 = byte_array_to_int(pres3)
#pres3 = decimal_exponent_one(pres3)
#pres3 = pascals_to_kilopascals(pres3)
print(f"Barometric pressure 3 : {round(pres3,2)} kPa")
return pres3
def read_temperature3(service3):
temp3_char = service3.getCharacteristics("e986145c-ead6-41a7-9718-d2b0b4834a11")[0]
temp3 = temp3_char.read()
temp3 = byte_array_to_int(temp3)
#temp3 = decimal_exponent_two(temp3)
print(f"temperature 3 : {round(temp3,2)} C")
return temp3
def loop():
c = data_3()
while True:
time.sleep(1.0)
print("\n")
read_temperature3(c)
read_pressure3(c)
t3 = read_temperature3(c)
p3 = read_pressure3(c)
r = BluetoothClient("DC:A6:32:4C:9D:ED", data_received_callback=None, port=2)
r.send(f"temp 3 : {t3} ")
r.send("\n")
r.send(f"pressure 3 : {p3} ")
#pause()
#time.sleep(1.0)
def main():
loop()
if __name__ == "__main__":
main()
Raspberry Pi Server code
from bluedot.btcomm import BluetoothServer
from signal import pause
def data_received(data):
print(data)
s.send(data)
s = BluetoothServer(data_received)
pause()
I am able to receive two readings and after that the client disconnects with the below error.
pi#raspberrypi:~/Desktop/rpible $ python3 onearduino_senddata.py
Connecting..
Discovering Services..
Discovering characteristics..
temperature 3 : 0 C
Barometric pressure 3 : 100 kPa
temperature 3 : 0 C
Barometric pressure 3 : 100 kPa
Traceback (most recent call last):
File "onearduino_senddata.py", line 83, in <module>
main()
File "onearduino_senddata.py", line 80, in main
loop()
File "onearduino_senddata.py", line 70, in loop
r = BluetoothClient("DC:A6:32:4C:9D:ED", data_received_callback=None, port=2)
File "/usr/local/lib/python3.7/dist-packages/bluedot/btcomm.py", line 567, in __init__
self.connect()
File "/usr/local/lib/python3.7/dist-packages/bluedot/btcomm.py", line 660, in connect
self._client_sock.connect((server_mac, self._port))
OSError: [Errno 16] Device or resource busy
please help to solve this issue.

Answer 1

Found the solution.
Create the client once outside the while loop and then the data transfer happens.
updated loop function.
def loop():
c = data_3()
//create the client connection here
r = BluetoothClient("DC:A6:32:4C:9D:ED", data_received_callback=None)
while True:
time.sleep(1.0)
print("\n")
t3 = read_temperature3(c)
p3 = read_pressure3(c)
r.send(f"temp 3 : {t3} ")
r.send("\n")
r.send(f"pressure 3 : {p3} ")