Improvements on preventing exceptions on an unstable connection

[corneyl]

• bridge.is_ready could be changed from the keep-alive thread, while the consume thread was sending commands. As a result an exception was thrown at limitlessled.group.commands.CommandV6.get_bytes() with as result that the consume thread was stopped. This is solved by adding a threading lock to bridge.is_ready.
• When disconnecting host or bridge on purpose, a socket error 'Errno 22: invalid arguments' was thrown. socket.error catch is added to _send_raw() to prevent daemon threads to stop.

[janLo]

Wouldn't it be better to have just one thread sending? Like the keepalive thread waiting on a timeouting conditional that is notified by the send() if something was put into the queue?

[corneyl]

That's also possible, but would it be really better? You continuously have to check the time to see whether the KEEP_ALIVE_TIME has passed. Now the keep alive thread just sleeps most of the time. Code would probably be better readable, but would it differ performance-wise?

[janLo]

Well, you can still have multiple threads for timeout sending and whatever but you should do the self._socket.send(...) either only from one thread or protect it with a lock, as a keepalive can happen at the same time as a command is send.

[happyleavesaoc]

I can't test on v6, so whenever you guys are satisfied with the changes, let me know and I'll merge.

[corneyl]

@happyleavesaoc Changes can be merged, tested for several days with this code and had no problems with permanent disconnects.

[corneyl]

Can this be merged? Thanks!

[happyleavesaoc]

Merged!

[corneyl]

Thanks! Made PR for it...