Get IP of selenium node the test is running on (example, written in PHP with Mink, but it can be achieved for other webdriver bindings too)

determineNodeIP.php

    /**
     * Determine the IP of the selenium node the test is running on
     *
     * @return string|null Returns IP as string or null if was not successful
     */
    function determineNodeIP($session, $seleniumhost, $seleniumport)
    {
        /**
         * @var $webdriver Selenium2Driver
         */
        $webdriver = $session->getDriver()

        $capabilities = $webdriver->getWebDriverSession()->capabilities();

        $sessionid = $capabilities['webdriver.remote.sessionid'];

        $json = file_get_contents(
            'http://' . $seleniumhost . ':' . $seleniumport
            . '/grid/api/testsession?session=' . $sessionid
        );

        $sessionInformation = json_decode($json, true);
    
        if (false === isset($sessionInformation['proxyId'])) {

            // Abort, the selenium host is a selenium standalone (expected: selenium grid)
            return null;
        }

        $ip = $matches[0];
        
        return $ip;
    }