蓝牙 Android RFCOMM/SPP 错误处理建议 [英] Bluetooth Android RFCOMM / SPP error handling suggestions

问题描述

我计划在 Android 设备和使用商业蓝牙模块的自定义传感器之间使用一种通信协议.我会使用据说向用户提供简单可靠的数据流，类似于 TCP"的 SPP 配置文件.

I am planning a communication protocol to be used between an Android device and a custom sensor that would use a commercial Bluetooth module. I would use the SPP profile that is said to "provide a simple reliable data stream to the user, similar to TCP."

我对蓝牙技术不太熟悉，对设计这样的协议有一些疑问.

I am not so familiar with the Bluetooth technology and have some questions about designing such a protocol.

首先，我不清楚我是否必须担心传输损坏的数据.底层协议栈是否会保证我从 InputStream Android 读取的字节与 UART 在传感器端接收的字节相同?我是否必须定义自己的受 CRC 或其他东西保护的数据包，否则会过大吗?

First of all it is not clear to me if I have to worry corrupted data being transferred or not. Will the underlying protocoll stack guarantee me that the bytes I read from the InputStream Android gives are the same that the UART receives on the sensor side? Do I have to define my own data packages protected with CRC or stuff or would it be overkill?

从 Android 蓝牙文档中我不清楚如果信号很弱并且丢失了一段时间，我的应用程序会发生什么.我是立即得到 IOException 还是平台为我提供了一些隐藏的错误处理和恢复，让我看不到这种短暂的中断?

It is not clear to me from the Android Bluetooth documentation what happens in my application if the signal is weak and is lost for a while. Do I get IOException at once or the platform provides me some hidden error handling and recovery that would make such short outages invisible to me?

感谢您的建议.

推荐答案

您不必担心 SPP 上的数据损坏，蓝牙提供 2 级 CRC，一种在基带，然后一种在 L2CAP 级别，两者都具有针对检测到的任何损坏的重传机制 - 因此应用程序将只收到良好的数据包.

You need not worry about data corruption over SPP , Bluetooth provides 2 levels of CRC , one at the baseband and then one at the L2CAP level, Both have retransmission mechanism for any detected corruptions - thus applications will receive only good packets.

关于第二个问题 - 在您连接的 Socket 流上是的，如果底层蓝牙连接断开，您将收到 IOExceptions，Android 无法处理自动恢复 - 通常应用程序需要检测断开连接的原因并尝试重新连接视情况而定.因此，如果您想从上次成功接收/发送的点开始继续数据交换，那么您的应用程序应该维护某种序列号和轻协议以实现恢复.另一种选择是在重新连接时简单地从数据交换开始(因此这取决于您的用例)

About the second question - Yes on the Socket streams that you are connected on you will receive IOExceptions if the underlying Bluetooth connections get disconnected, Android cannot handle automatic restore - typically applications need to detect the reason for disconnection and try re-connect as applicable. So if you want to continue your data exchange from the point you last successfully received / sent then for it your application should maintain some sort of sequence number and light protocol to achieve a resume. The other option is to simply start from the beaning of data exchange upon a re-connect (So it depends on your usecase)

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