Hi! In this PR I added support for specifying the timeout used in sockets via an argument.
I changed the use of select syscall to poll syscall. Select syscall has a known limitation:

WARNING: select() can monitor only file descriptors numbers that
are less than FD_SETSIZE (1024)—an unreasonably low limit for
many modern applications—and this limitation will not change.
All modern applications should instead use poll(2) or epoll(7),
which do not suffer this limitation.

Taken from https://man7.org/linux/man-pages/man2/select.2.html

I also make the BaseDisplay class public because it can be useful to connect to a X11 server without making several requests to get all the extensions available.

I also added a check in parse_connection_setup method that checks if the response has a valid status. In the protocol specification page 11 and 114 you can see all the available status (0, 1 or 2).

I ran the tests with python3 runtests.py and all passed.

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XML: /com.docker.devenvironments.code/nosetests.xml
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Ran 524 tests in 12.184s

OK (SKIP=142)

I hope you can merge my changes. Any question feel free to ask.