從“掛起”藍牙 python 連接中檢測和恢復

Question

我使用 RPi 內置模塊和 Arduino 上的 HC-05 模塊在 Raspberry Pi 3b+ 和 Arduino Mega 之間建立了藍牙連接。 雙向溝通就像一個魅力，幾分鍾到有時，一次幾個小時。

然后，在看似隨機的時間，python 代碼掛起，被sock.recv() function 阻塞。 我可以通過 ctrl-c 殺死它，然后重新啟動它，它通常會毫無問題地重新連接。

我知道藍牙有點挑剔，所以雖然任何關於如何使通信更加健壯和延長運行時直到掛起的建議都值得贊賞，但我更感興趣的是如何檢測這種“掛起”並從中恢復它。 即：我只想終止連接並嘗試從 Python 程序中重新連接，而不是我自己必須看到並對此做出反應。

這是我迄今為止在 python 中所擁有的：

#!/usr/bin/python3

import datetime
import socket
import sys
import time

import bluetooth

COMMAND_START_CHAR = '<'
COMMAND_END_CHAR = '>'
LOGFILE = 'bt.log'


def SearchForFullCommand(buffer):
  """Puts fully formed commands from buffer into a list, returning the remaining buffer.

  We expect commands to be demarcated by COMMAND_START_CHAR and COMMAND_END_CHAR.  The
  buffer may have zero or more such commands. This function finds all demarcated commands,
  strips off those demarcations, and returns the remaining buffer.  Any text that arrives
  before a COMMAND_START_CHAR is discarded.

  Args:
    buffer: string representing the text received so far.

  Returns:
    A 2-tuple, where the first element is the remaining buffer, and the second element
    is a potentially empty list of identified commands.
  """
  commands = []
  while COMMAND_END_CHAR in buffer:
    end_pos = buffer.find(COMMAND_END_CHAR)
    if COMMAND_START_CHAR in buffer[:end_pos]:
      start_pos = buffer.find(COMMAND_START_CHAR) + len(COMMAND_START_CHAR)
      commands.append(buffer[start_pos:end_pos])
    buffer = buffer[end_pos+len(COMMAND_END_CHAR):]
  return (buffer, commands)  # no command found


def Log(s):
  """Appends message s to the logfile."""
  with open(LOGFILE, 'a') as f:
    f.write('%s\n' % s)


def ConnectBluetooth(address, port):
  """Attempts to make one connection to the given address and port."""
  sock = bluetooth.BluetoothSocket(bluetooth.RFCOMM)
  sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
  try:
    sock.connect((address, port))
  except (bluetooth.btcommon.BluetoothError) as e:
    Log('Failed to connect: %s' % e)
    return None
  return sock


def ConnectBluetoothRetry(address, port, seconds):
  """Attempts to make connections for a number of seconds, exiting program on fail."""
  second = 0
  while second < seconds:
    sock = ConnectBluetooth(address, port)
    if sock:
      Log('Connected after %d seconds' % second)
      return sock
    time.sleep(1)
    second += 1
  Log('Failed to connect after %d seconds' % second)
  sys.exit()


def main():
  """Sends sequential numbers over bluetooth, and receives & parses anything sent."""
  sys.stderr = open(LOGFILE, 'a')

  start = time.time()
  timestring = datetime.datetime.fromtimestamp(start).strftime('%Y-%m-%d %H:%M:%S')
  Log('Started at %s' % timestring)

  bd_addr = '98:D3:11:FC:42:16'
  port = 1
  sock = ConnectBluetoothRetry(bd_addr, port, 10)

  buffer = ''
  x = 0

  while True:
    try:
      recv = sock.recv(1024)
    except (bluetooth.btcommon.BluetoothError) as e:
      Log('Failed to receive: %s' % e)
      sock.close()
      sock = ConnectBluetoothRetry(bd_addr, port, 10)
    Log('.. %s (len=%d) after running for %.3f hours' % (
        recv, len(recv), (time.time() - start) / 60**2))
    buffer += recv.decode()
    buffer, commands = SearchForFullCommand(buffer)
    if commands:
      for n, command in enumerate(commands):
        Log('Received full command #%d: %s' % (n, command))

    send = COMMAND_START_CHAR+str(x)+COMMAND_END_CHAR
    try:
      sock.send(send)
    except (bluetooth.btcommon.BluetoothError) as e:
      Log('Failed to send %s: %s' % (send, e))
      sock.close()
      sock = ConnectBluetoothRetry(bd_addr, port, 10)
    Log('Sent %s' % send)

    x += 1
    time.sleep(1)


main()

運行良好時，python 日志文件如下所示：

.. b'646>' (len=4) after running for 0.843 hours
Received full command #0: 646
Sent <2526>
.. b'<647>' (len=5) after running for 0.843 hours
Received full command #0: 647
Sent <2527>
.. b'<' (len=1) after running for 0.844 hours
Sent <2528>
.. b'648>' (len=4) after running for 0.844 hours

然后，注意到它已經停止工作，我將其殺死，然后重新啟動它：

KeyboardInterrupt
Started at 2020-05-03 11:15:07
Failed to connect: [Errno 16] Device or resource busy
Failed to connect: [Errno 16] Device or resource busy
Failed to connect: [Errno 16] Device or resource busy
Failed to connect: [Errno 16] Device or resource busy
Failed to connect: [Errno 16] Device or resource busy
Failed to connect: [Errno 16] Device or resource busy
Failed to connect: [Errno 16] Device or resource busy
Failed to connect: [Errno 16] Device or resource busy
Failed to connect: [Errno 16] Device or resource busy
Failed to connect: [Errno 16] Device or resource busy
Failed to connect after 10 seconds

我再試試：

Started at 2020-05-03 11:15:42
Failed to connect: [Errno 112] Host is down
Failed to connect: [Errno 112] Host is down
Failed to connect: [Errno 112] Host is down
Connected after 3 seconds
.. b'1146><1147><1148><1149><1150><1151><1152><1153><1154><1155><1156><1157><1158><1159><1160><1161><1162><1163><1164><1165><1166><1' (len=127) after running for 0.005 hours
Received full command #0: 1147
Received full command #1: 1148
Received full command #2: 1149

...它又運行了一兩個小時，然后再次掛起。 我沒有在物理上移動發送者或接收者 - 它們彼此相距一英尺 - 所以它不是范圍。 雖然我嘗試斷開 Arduino 並重新啟動它，但它們在仍在運行的 Python 進程中重新連接沒有問題。

Arduino 代碼雖然我認為它不相關，但在這里：

long n = 1;

void setup() 
{
    Serial.begin(9600);

    // HC-05 default serial speed for communcation mode is 9600
    Serial1.begin(9600);  
}

void loop() 
{
    Serial1.print("<");
    Serial1.print(n);
    Serial1.print(">");
    if(Serial1.available() > 0){ // Checks whether data is comming from the serial port
      Serial.println(Serial1.readString());} // Reads the data from the serial port
    delay(1000);
    n++;
}

感謝您的任何幫助或建議！

Answer 1

盡管幾天不同的方法和努力，我無法讓套接字連接持續超過幾個小時； 我只去了套接字兔子洞，因為我無法弄清楚如何通過藍牙使用 pySerialTransfer，甚至只是串行。

所以，回到串行方法，經過更多的努力和調查，我最終能夠讓這種方法在 Arduino 上的 Raspberry Pi 和 HC-05 之間實現穩定的（此時超過 1 天）藍牙連接。

代碼在這里。