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Detecting bluetooth device disconnects/crashes

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#57 1 comment 2 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
30/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
javascript, node.js
Domain
embedded-iot, networking

Research direction

Start with lib/connection.js and inspect the read callback, including how zero-length buffers and read errors are emitted. Reproduce the Bluetooth shutdown behavior described in the issue and determine the expected disconnect event and timing. Done means the disconnect behavior is defined and covered without assuming zero-length buffers are impossible during a valid connection.

Written by the indexing model from the issue text.

Description

Hi!
I couldn't find a way to detect if a connection has crashed or disconnected so I tried to implement my own.
In lib/connection.js, I noticed that - if I printed the chunks of the read method - they stop printing as soon as I turn off my bluetooth device; after ~20seconds of apparent frozen behavior, this method continued working, printing chunks of zero length buffers.
Thus, I added the following line
if(chunk.length == 0){ self.emit('error')}
in

(function read(){
      self.isOpen() && self.port.read((err, chunk) => {
        process.nextTick(read);
        if(err) return self.emit('error', err);
        self.emit('data', chunk);
        if(chunk.length == 0){ self.emit('error')}
      });
    })();

This allows me to fetch error events like so:

    connect(address, 1, (err, linkage) => {
      if (err) {
        console.log('connection attempt error');
      } else {
        linkage.on('error', (err) => {
          console.log('disconnected!);
        });
      }
    )}

However my approach assumes I won't be receiving zero length buffers when connected which I realize that might not always be true (or not for all devices);
Also, any thoughts on how to detect the disconnect before the ~20seconds pass?
Thanks!

Dominant language
C++
Stars
205
Forks
56
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