Android-SerialPort-API | open source Android serial communication Demo and modify | Wrapper library

I have a very peculiar problem. In android I am using FileInputStream to read from the serial (ttySx/COM) port. I am using this to decide which of the known devices is connected (if any at all). What I basically do is:

1. Are you device 1? No...
2. Are you device 2? No...
3. Are you device 3? Yes...
4. Great lets do some stuff...

And this works great. If there is any incoming data to read (response from device), everything is fine. However, if there is no device connected to ttySx there is nothing to respond to my write. That means nothing to read.

Now, FileInputStream.read() is a blocking call. When I call it in the thread, thread is effectively frozen. I cannot interrupt the thread because for that I would have to read something first. So far everything makes perfect sense.

As there is no response from the port for quite some time I decide that there is nothing connected and want to stop reading and dispose of the thread(actually I do not want to bother with the port anymore because with nothing connected, it is useless to me at this moment). As mentioned earlier interrupt itself is no good. What should be working, is to close() the FileInputStream (read() will throw an exception and hooray!). The close() works... As long as the read() read anything ever (like when I had an answering device connected, then disconnect it -> read() is stuck - because no data to read - but close() works).

However if there was not a thing connected to the port when the read() started (equals: I haven't read a single byte), the close() method does nothing. It does not close the stream. Nor does work the closing of FileInputStream channel.

I could create a workarround: Store the FileInputStream somewhere and when I want to read from the port again later, use the same instance. That would work for me. Unfortunately I would quite unnecessarily block the port itself. No other process (for example another application) could read from the port because it is stuck in "uninterruptable" read...

Any ideas why this is happening and how to make it right? Or some other way to detect if there is anything connected to the ttySx port?

Thanks.

EDIT1: The library used for communication with serial port is https://github.com/cepr/android-serialport-api