Multi-Threaded api.connect() not working in Ubuntu Linux

[cbeytas]

vncdotool v1.0.0, python 3.8.10, twisted 20.3.0 and 21.2.0

A simple VNC connection attempt works fine under Windows but when run on Linux (Ubuntu 20.04) it fails to establish a TCP connection. The connection starts, but never progresses. Seems to be a Twisted reactor issue.

In ThreadedVNCClientProxy api.py line 77 it uses reactor.callWhenRunning. This is not thread-safe. The reactor has already been started so it has the same effect of just calling factory_connect directly from the main thread.

Wrapping it in reactor.callFromThread fixed the issue for me:
reactor.callFromThread(reactor.callWhenRunning, factory_connect, self.factory, host, port, family)

import vncdotool.api
vnc = vncdotool.api.connect(server)
print(vnc.protocol)
None