If your C# client cannot establish this initial local HTTP handshake with the freshly started geckodriver.exe process within a default 2-second timeout window, the runtime throws the exception. 5 Common Causes and Their Solutions
System-wide proxy settings or a missing 127.0.0.1 entry in the hosts file can block the local connection.
service = FirefoxDriverService.CreateDefaultService(@"C:\path\to\geckodriver\folder"); FirefoxDriver(service); Use code with caution. Copied to clipboard 4. Check Local Network/Hosts Settings The driver service needs to bind to If your C# client cannot establish this initial
Sometimes, if you stop debugging abruptly, the geckodriver.exe process stays running in the background. When you try to run the code again, it tries to bind to the same localhost port, fails, and throws this error.
Your C# code then attempts to ping this port to ensure the driver is alive and ready to receive commands. Copied to clipboard 4
If the driver service cannot bind to localhost , a firewall or another application might be actively blocking the port. Additionally, if your code attempts to start multiple parallel threads on the exact same port, the second instance will throw an exception.
Always implement proper disposal patterns to prevent resource leaks: Your C# code then attempts to ping this
Navigate to the tab and click Environment Variables . Under System variables , select New .
public void Dispose()