I am using chrome driver 2.35(tried till v 2.9) and chrome browser v 65.
gems used: watir 6.10.3 selenium-webdriver 3.11.0
error message:
Selenium::WebDriver::Error::WebDriverError: unable to connect to chromedriver 127.0.0.1:9515
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/selenium-webdriver-3.11.0/lib/selenium/webdriver/common/service.rb:142:in `connect_until_stable'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/selenium-webdriver-3.11.0/lib/selenium/webdriver/common/service.rb:72:in `block in start'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/selenium-webdriver-3.11.0/lib/selenium/webdriver/common/socket_lock.rb:39:in `locked'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/selenium-webdriver-3.11.0/lib/selenium/webdriver/common/service.rb:69:in `start'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/selenium-webdriver-3.11.0/lib/selenium/webdriver/chrome/driver.rb:42:in `initialize'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/selenium-webdriver-3.11.0/lib/selenium/webdriver/common/driver.rb:44:in `new'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/selenium-webdriver-3.11.0/lib/selenium/webdriver/common/driver.rb:44:in `for'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/selenium-webdriver-3.11.0/lib/selenium/webdriver.rb:85:in `for'
from C:/Ruby23/lib/ruby/gems/2.3.0/gems/watir-6.10.3/lib/watir/browser.rb:48:in `initialize'
I downgraded the chrome version to 62 and disabled auto update to resolve this issue. Older version available here Before installing the older version some steps needs to be followed.