Add support for "port 0" dynamic port allocation

[vflegel-sib]

Background:

• Under Linux and Windows, bind()-ing to network port 0 assigns the application a free port from the dynamic port range.

Test setup:

• Selenium server standalone version 2.48.2
• CentOS 7
• Java 1.7.0_91
• Firefox 38.3.0

Issue description:

• When launching multiple Selenium instances on "HtmlSuites" it can be very useful for a user to be able to set the option -port 0. This would allow the Selenium application to receive a free port from the OS, removing the burden of finding one from the user's shoulders.
• The tested Selenium server accepts -port 0 option and will correctly listen on the random free port offered by the OS, as can be seen via lsof.
• The automatically generated configuration files for the browser (here: Firefox) do not reflect this assigned port but reference the port set via command-line: 0.

Example:

Selenium command used, i.e. with your own favourite HtmlSuite:

java -jar selenium-server-standalone.jar -port 0 -htmlSuite "*firefox" "http://some.url.ch/" "test_suite.html" "results.html"

Launching lsof -p <pID> on the process ID will show the listening port:

[...]
java    9500 jenkins   11u  IPv6             190573       0t0      TCP *:51276 (LISTEN)
[...]

When looking at the prefs.js file generated for the Firefox instance, we can see that the URL wrongly references localhost:0 instead of localhost:51276 (URL %XX notation removed for readability):

[...]
user_pref("browser.startup.homepage", "chrome://src/content/TestRunner.html?auto=true&multiWindow=true&defaultLogLevel=info&baseUrl=http://some.url.ch/&resultsUrl=../postResults&test=http://localhost:0/selenium-server/tests/test_suite.html");
[...]

Possible resolution:

• I'm not a programmer but the Java socket documentation has a getLocalPort function which could be used to identify the effective port number on which Selenium is listening. This value should then override the command-line value.

This would really help in our current setup of Selenium test cases :-)

Kind regards,
Volker

[lukeis]

selenium RC / selenese (htmlSuite) is deprecated and no longer receiving support here.

I recommend migrating your test suite to use WebDriver instead. In the near future we will be 'freezing' this code into a "legRC" jar and stripping it out of the code base.