使用 rfcomm 检查连接是否成功

Question

我正在尝试使用蓝牙加密狗将手机连接到RaspberryPi(不要尝试做任何惊天动地的事情，只需确定我的手机何时在该区域(。如果我打开手机的蓝牙并发出以下命令，我会得到以下输出(在任何人开始向我宣扬这是如何违反安全性之前，让我提醒您，这不是我的实际手机蓝牙 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，如果我关闭手机的蓝牙并发出相同的命令，我会得到以下输出(同样，所有 id 都已更改以保护无辜者(。

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内以及何时离开，因此我需要某种方式(其他方式(来检测加密狗何时可以连接和无法连接到它。我怎样才能实现这一目标？(注意：我尝试将手机从建筑物中取出，甚至将其完全关闭(

编辑：我已经考虑过捕获stderr消息并像这样测试它

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

我还没有完全弄清楚如何做到这一点，但这就是我绕过它的方式。我只需在sudo rfcomm connect 0 AA:BB:CC:DD:EE:FF 10命令后等待 5 秒钟，然后检查是否有连接。我怀疑这实际上非常有效，因为下一次迭代会捕获所犯的任何错误，但不要引用我的话。也许更多的体验.我已经包含了最小工作示例(MWE(，以便您可以遵循它。

女工程师：

#!/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