Getting error when using selenium-webdriver to automate CEF application

[Xuemin Yin]

I'm using selenium-webdriver to automate a CefSharp (CEF3) based application, but kept getting errors.

I use the following Ruby scripts to launch the CEF application:

require "selenium-webdriver"
cefpath = 'C:\mypathto\cefapp.exe'
Selenium::WebDriver::Chrome.path = cefpath
browser = Selenium::WebDriver.for :chrome
......

When running it, it does open the CEF application (a container of Chrome), but then gets stuck with the following error:

C:/Ruby200/lib/ruby/2.0.0/net/protocol.rb:158:in `rescue in rbuf_fill': Net::ReadTimeout (Net::ReadTimeout)
from C:/Ruby200/lib/ruby/2.0.0/net/protocol.rb:152:in `rbuf_fill'
from C:/Ruby200/lib/ruby/2.0.0/net/protocol.rb:134:in `readuntil'
from C:/Ruby200/lib/ruby/2.0.0/net/protocol.rb:144:in `readline'
from C:/Ruby200/lib/ruby/2.0.0/net/http/response.rb:39:in `read_status_line'
from C:/Ruby200/lib/ruby/2.0.0/net/http/response.rb:28:in `read_new'
from C:/Ruby200/lib/ruby/2.0.0/net/http.rb:1406:in `block in transport_request'
from C:/Ruby200/lib/ruby/2.0.0/net/http.rb:1403:in `catch'
from C:/Ruby200/lib/ruby/2.0.0/net/http.rb:1403:in `transport_request'
from C:/Ruby200/lib/ruby/2.0.0/net/http.rb:1376:in `request'
from C:/Ruby200/lib/ruby/2.0.0/net/http.rb:1369:in `block in request'
from C:/Ruby200/lib/ruby/2.0.0/net/http.rb:852:in `start'
from C:/Ruby200/lib/ruby/2.0.0/net/http.rb:1367:in `request'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver/remote/http/default.rb:83:in `response_for'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver/remote/http/default.rb:39:in `request'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver/remote/http/common.rb:40:in `call'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver/remote/bridge.rb:634:in `raw_execute'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver/remote/bridge.rb:99:in `create_session'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver/remote/bridge.rb:68:in `initialize'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver/chrome/bridge.rb:29:in `initialize'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver/common/driver.rb:37:in `new'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver/common/driver.rb:37:in `for'
from C:/Ruby200/lib/ruby/gems/2.0.0/gems/selenium-webdriver-2.42.0/lib/selenium/webdriver.rb:67:in `for'

Any idea why?

Thanks a lot.