Let’s go through the most common culprits, from most to least likely.
You can explicitly force the GeckoDriverService to use the IPv4 loopback address ( 127.0.0.1 ) instead of the word localhost .
driver.Navigate().GoToUrl("https://www.google.com"); Let’s go through the most common culprits, from
This error occurs precisely when your C# code attempts to initialize a new FirefoxDriver instance. The system tries to launch a local HTTP service for communication between your test framework and the GeckoDriver (the executable that bridges Selenium with Firefox), but this service fails to start properly. The port number in the error message changes with every execution—your system is trying to find an available port, but something in your environment is blocking or disrupting that process.
Open Task Manager and end all geckodriver.exe tasks. The system tries to launch a local HTTP
// 3. Pass the service to the driver constructor IWebDriver driver = new FirefoxDriver(service);
The default timeout for HTTP communication with GeckoDriver is 60 seconds. If your system is under heavy load, GeckoDriver may require more time to start up. A timeout that’s too short can cause the driver service to fail before it fully initializes. Let’s go through the most common culprits, from
driver = webdriver.Firefox()
In CI/CD environments, implement a retry mechanism that waits a few seconds and retries driver initialization if the first attempt fails.