在 Raspberry Pi 和计算机之间使用带有 Python 套接字库的蓝牙串行端口配置文件发送数据

Question

I have been able to connect a sensor via Bluetooth to my Raspberry Pi and receive its information with the Serial Port Profile using the Python Socket library with this program:

import socket

sensorMACAddress = 'XX:XX:XX:XX:XX:XX'

port = 1

s = socket.socket(socket.AF_BLUETOOTH, socket.SOCK_STREAM, socket.BTPROTO_RFCOMM)
s.connect((sensorMACAddress,port))

s.send(bytes('#ob', 'UTF-8'))  # Tells the sensor to send the data in bytes

while(1):

   data = s.recv(12)


   while len(data) < 12:

       data = data + s.recv(12)


   Y = struct.unpack('<f', data[0:4])[0]
   P = struct.unpack('<f', data[4:8])[0]
   R = struct.unpack('<f', data[8:12])[0]

   YPR = str(['S3', int(Y), int(P), int(R)])

   print(YPR)
   print('\n')

(The sensor sends the data automatically once connected.)

Now I want to send the information of this sensor to my computer, so I just updated the prior program by creating a new socket object for the connection between the Raspberry and the computer to send the information with the send() function:

# This goes outside the loop
computerMACAddress = 'XX:XX:XX:XX:XX:XX'
s_comp = socket.socket(socket.AF_BLUETOOTH, socket.SOCK_STREAM, socket.BTPROTO_RFCOMM)
s_comp.connect((computerMACAddress,port))


# This goes inside the loop
s_comp.send(YPR.encode())

Apparently this program is sending information, and it does connect via Bluetooth to my computer (or my phone) but my computer (Windows) doesn't seem to receive it, and neither does my phone (Android).

Following this steps ( https://scribles.net/setting-up-bluetooth-serial-port-profile-on-raspberry-pi/ ) I was able to send and receive information between my Raspberry Pi and my computer via Bluetooth using their respective keyboards, using the Bluetooth Serial Port Profile, so the problem seems to be on the sockets and not on the Bluetooth Serial Port Profile connection. The following simple program didn't work either:

import socket

computerMACAddress = 'XX:XX:XX:XX:XX:XX'

port = 1

s = socket.socket(socket.AF_BLUETOOTH, socket.SOCK_STREAM, socket.BTPROTO_RFCOMM)
s.connect((computerMACAddress,port))


data = 'Hello world!'

while 1:
   s.send(bytes(data, 'UTF-8'))
   print(data)

On this example ( http://blog.kevindoran.co/bluetooth-programming-with-python-3/ ) I saw that they create a client program to send the information and a server program to receive it, but I didn't have to do this to receive information from the sensor to the Raspberry, so I don't know why I would need to do it with the computer. In any case, I tried but I couldn't make it work. Apparently, sockets don't work very well in Windows, but with my Android phone I couldn't receive information either, even though I could establish a Bluetooth connection.

So, in summary:

1. Why did the send() and recv() functions work with the sensor but not with the computer or phone?
2. If I need a server program, why didn't I need it to receive information from the sensor, and how can I make it work?
3. If that's not the problem, what is it?

Thank you.

Answer 1

It looks like there is a Bluetooth Serial Port Profile (SPP) server running on the sensor and so the SPP client on the Raspberry Pi connects and exchanges information successfully.

Python sockets for Bluetooth SPP on Windows was only introduced in Python 3.9 so you will need a recent version of Python on your Windows computer.

However, if it has connected, then maybe you need to go hunting for the serial port it has connected it to. Maybe the following will help: https://www.instructables.com/Raspberry-Pi-Bluetooth-to-PuTTY-on-Windows-10/

However a more typical setup would be that the Raspberry Pi would be a bridge between the sensor and the network. This means that the value from the sensor goes to the RPi by Bluetooth. Then the RPi makes the sensor data available over WiFi/internet via a website/socket running on the RPi.

As a side note, you could be a little more efficient with your unpacking of the data. For example:

>>> data = b'\x11\x11\x11\x11\x22\x22\x22\x22\x33\x33\x33\x33'
>>> import struct
>>> Y, P, R = struct.unpack('<fff', data)
>>> print(f"['S3', {Y}, {P}, {R}]\n")
['S3', 1.1443742118159064e-28, 2.1973163753312686e-18, 4.17232506322307e-08]