If something happens to the socket we should try bind back to Gecko and try reuse the session. If it fails then we should leave it to the user to correct See log from Selenium Proxy where the unexpected disconnect then causes exceptions to tell the user to create a new session 2012-05-24 12:12:51,612 - Selenium-Proxy - DEBUG - /url - {u'url': u'http://localhost:8012/formPage.html', u'sessionId': u'13'} - 13 - None 1800 2012-05-24 12:12:51,612 - Selenium-Proxy - INFO - Navigating to http://localhost:8012/formPage.html - 13 1801 2012-05-24 12:12:51,885 - Selenium-Proxy - DEBUG - /element - {u'using': u'name', u'sessionId': u'13', u'value': u'there is no spoon'} - 13 - None 1802 2012-05-24 12:12:51,885 - Selenium-Proxy - INFO - Find Element using - name, value - there is no spoon - 13 1803 2012-05-24 12:15:51,890 - Selenium-Proxy - CRITICAL - Server Exception: Traceback (most recent call last): 1804 File "selenium_proxy.py", line 216, in do_POST 1805 value={'ELEMENT': str(self.server.marionette.find_element(body['using'], body['value'], id=element))}) 1806 File "/Users/davidburns/.virtualenvs/seleniumproxy/lib/python2.7/site-packages/marionette-0.2-py2.7.egg/marionette/marionette.py", line 343, in find_element 1807 response = self._send_message('findElement', 'value', **kwargs) 1808 File "/Users/davidburns/.virtualenvs/seleniumproxy/lib/python2.7/site-packages/marionette-0.2-py2.7.egg/marionette/marionette.py", line 163, in _send_message 1809 raise TimeoutException(message='socket.timeout', status=21, stacktrace=None) 1810 TimeoutException: socket.timeout 1811 1812 2012-05-24 12:15:51,921 - Selenium-Proxy - DEBUG - /url - {u'url': u'http://localhost:8012/formPage.html', u'sessionId': u'13'} - 13 - None 1813 2012-05-24 12:15:51,922 - Selenium-Proxy - INFO - Navigating to http://localhost:8012/formPage.html - 13 1814 2012-05-24 12:15:51,932 - Selenium-Proxy - CRITICAL - Server Exception: Traceback (most recent call last): 1815 File "selenium_proxy.py", line 301, in do_POST 1816 assert(self.server.marionette.navigate(body['url'])) 1817 File "/Users/davidburns/.virtualenvs/seleniumproxy/lib/python2.7/site-packages/marionette-0.2-py2.7.egg/marionette/marionette.py", line 265, in navigate 1818 response = self._send_message('goUrl', 'ok', value=url) 1819 File "/Users/davidburns/.virtualenvs/seleniumproxy/lib/python2.7/site-packages/marionette-0.2-py2.7.egg/marionette/marionette.py", line 145, in _send_message 1820 raise MarionetteException(message="Please start a session") 1821 MarionetteException: Please start a session 1822 1823 2012-05-24 12:15:51,953 - Selenium-Proxy - DEBUG - /url - {u'url': u'http://localhost:8012/formPage.html', u'sessionId': u'13'} - 13 - None 1824 2012-05-24 12:15:51,953 - Selenium-Proxy - INFO - Navigating to http://localhost:8012/formPage.html - 13 1825 2012-05-24 12:15:51,954 - Selenium-Proxy - CRITICAL - Server Exception: Traceback (most recent call last): 1826 File "selenium_proxy.py", line 301, in do_POST 1827 assert(self.server.marionette.navigate(body['url'])) 1828 File "/Users/davidburns/.virtualenvs/seleniumproxy/lib/python2.7/site-packages/marionette-0.2-py2.7.egg/marionette/marionette.py", line 265, in navigate 1829 response = self._send_message('goUrl', 'ok', value=url) 1830 File "/Users/davidburns/.virtualenvs/seleniumproxy/lib/python2.7/site-packages/marionette-0.2-py2.7.egg/marionette/marionette.py", line 145, in _send_message 1831 raise MarionetteException(message="Please start a session") 1832 MarionetteException: Please start a session 1833

Do you have a link to the test case that produced this error?

In this case it is a test case with an implicit wait for an element that will never be there. The implicit wait never throws and then the socket to Gecko times out

This test passes locally now, so I've added it to the manifest and pushed it to try: https://tbpl.mozilla.org/?tree=Try&rev=679e219d29e2

try is green!