[rb] Waiting till Socket connection completed

[N0xFF]

After select we should use getsockopt to read the SO_ERROR option at
level SOL_SOCKET to determine that connection completed successfully. Otherwise in connect_nonblock we can get EISCONN error.

http://man7.org/linux/man-pages/man2/connect.2.html

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This change is 

[N0xFF]

This is reason why I all time get error

Errno::ECONNREFUSED: Failed to open TCP connection to 127.0.0.1:9515 (Connection refused - connect(2) for "127.0.0.1" port 9515)

and can't run Ruby on Rails system tests on WSL.

[twalpole]

While I believe this PR is technically more correct, I fail to see how it fixes any Errno::ECONNREFUSED issue you're having?

[N0xFF]

selenium/rb/lib/selenium/webdriver/common/socket_poller.rb

Lines 79 to 82 in 361c731

	begin
	sock.connect_nonblock sockaddr
	rescue Errno::EINPROGRESS
	retry if IO.select(nil, [sock], nil, CONNECT_TIMEOUT)

Errno::EINPROGRESS error means that connection in progress and we need to check status to make a decision. We check that socked is writable via IO.select and retry connection. But connection is not ready and next we got Errno::EALREADY error.

It was caught by

selenium/rb/lib/selenium/webdriver/common/socket_poller.rb

Lines 84 to 89 in 361c731

	rescue *CONNECTED_ERRORS
	# yay!
	end
	sock.close
	true

So listening? returns true. That allow commands by webdriver. But connection still not ready and finally we got Errno::ECONNREFUSED that not handled.

[N0xFF]

Now we check conn_completed? otherwise raise Errno::ECONNREFUSED. It will be catched in

selenium/rb/lib/selenium/webdriver/common/socket_poller.rb

Lines 90 to 94 in 361c731

	rescue *NOT_CONNECTED_ERRORS
	sock.close if sock
	WebDriver.logger.debug("polling for socket on #{[@host, @port].inspect}")
	false
	end

So listening? returns false and listening? is retry with new connection in with_timeout block.

selenium/rb/lib/selenium/webdriver/common/socket_poller.rb

Lines 38 to 40 in 361c731

	def connected?
	with_timeout { listening? }
	end

[twalpole]

Ok - makes sense -- do you have time to fix the conflicts here so it's mergeable?

[N0xFF]

Done. But after merge I found other problem #7010

[twalpole]

Thanks.