使用rfcomm检查是否成功连接

Question

我正试图用蓝牙线将我的手机连接到我的RaspberryPi上(不想做任何破坏地球的事情，只要确定我的手机什么时候在这个区域)。如果我在上打开手机的蓝牙并发出以下命令，我将得到以下输出(在任何人开始向我讲述这是如何破坏安全之前，让我提醒您，这是而不是的实际电话蓝牙id)：

命令：

sudo rfcomm connect 0 AA:BB:CC:DD:EE:FF 10
echo $?

输出：

Connected /dev/rfcomm0 to AA:BB:CC:DD:EE:FF on channel 10
Press CTRL-C for hangup
0

现在，如果我将手机的蓝牙关闭，并发出相同的命令，我将得到以下输出(同样，所有id都已被更改以保护无辜)。

命令：

sudo rfcomm connect 0 AA:BB:CC:DD:EE:FF 10
echo $?

输出：

Can't connect RFCOMM socket: Host is down
0

由于我试图确定手机何时在房间里，何时离开，我需要一些方法(其他方式)来检测何时可以和不能连接到它。我怎样才能做到这一点呢？(注意:我试着把电话从大楼里移开，甚至把它完全关掉)

编辑：--我已经考虑过捕获stderr消息并进行如下测试

error=$`sudo rfcomm connect 0 AA:BB:CC:DD:EE:FF 10 >/dev/null` &
if [ $error=="Can't connect RFCOMM socket: Host is down" ]
then
    ...
fi;

但问题是rfcomm必须在后台运行。

Answer 1

我还没弄清楚该怎么做，但我就是这么做的。我只需在sudo rfcomm connect 0 AA:BB:CC:DD:EE:FF 10命令之后等待5秒，然后检查是否存在连接。我怀疑这实际上是完美的，因为下一次迭代将捕捉到所犯的任何错误，但不要引用我的话。也许更有经验。我已经包含了最小工作示例(MWE)，这样您就可以遵循它。

MWE:

#!/bin/bash

phone1="AA:BB:CC:DD:EE:FF" #Address of phone
inside=1  # Whether the phone is 'inside' the house (0) or 'outside (1)

phoneDetected ()
{
   # Search for phone
   hcitool rssi $phone1 &>/dev/null
   ret=$?

   # If search was unsuccessful,
   if [ $ret -ne 0 ]
   then
      # Add phone
      sudo rfcomm connect 0 $phone1 10 &>/dev/null &

      # Note: the return code of rfcomm will almost always be 0,
      # so don't rely on it if you are looking for failed connections,
      # instead wait 5 seconds for rfcomm to connect, then check
      # connection again. Note this is not fool proof as an rfcomm
      # command taking longer than 5 seconds could break this program,
      # however, it generally only takes 2 seconds.
      sleep 5
      hcitool rssi $phone1 &>/dev/null
      ret=$?
   fi;

   # Case 1) we are now connected (ret=0) and we were previously outside (inside=1)
   if [ $ret -eq 0 ] && [ $inside -eq 1 ]
   then
      # change state to inside and do something (I am playing a song)
      inside=0
      mplayer /home/pi/documents/rasbpi/raspi1/media/audio/1.mp3 &>/dev/null
   # Case 2) we are no longer connected (ret=1) but we were previously inside (inside=0)
   elif [ $ret -eq 1 ] && [ $inside -eq 0 ]
   then
      # change state to outside and do something (I am playing another song)
      inside=1
      mplayer /home/pi/documents/rasbpi/raspi1/media/audio/2.mp3 &>/dev/null
   fi;
}

# run an infinite loop
while :
do
   phoneDetected $phone1
done