[🐛 Bug]: [dotnet] Cannot start the driver service when `FirefoxDriverService.LogPath` is set

[nvborisenko]

Description

Unhandled exception. OpenQA.Selenium.WebDriverException: Cannot start the driver service on http://localhost:56837/
   at OpenQA.Selenium.DriverService.Start() in D:\SeleniumHQ\selenium\dotnet\src\webdriver\DriverService.cs:line 259
   at OpenQA.Selenium.Remote.DriverServiceCommandExecutor.ExecuteAsync(Command commandToExecute) in D:\SeleniumHQ\selenium\dotnet\src\webdriver\Remote\DriverServiceCommandExecutor.cs:line 118
   at OpenQA.Selenium.WebDriver.ExecuteAsync(String driverCommandToExecute, Dictionary`2 parameters) in D:\SeleniumHQ\selenium\dotnet\src\webdriver\WebDriver.cs:line 585
   at OpenQA.Selenium.WebDriver.Execute(String driverCommandToExecute, Dictionary`2 parameters) in D:\SeleniumHQ\selenium\dotnet\src\webdriver\WebDriver.cs:line 567
   at OpenQA.Selenium.WebDriver.StartSession(ICapabilities capabilities) in D:\SeleniumHQ\selenium\dotnet\src\webdriver\WebDriver.cs:line 627
   at OpenQA.Selenium.WebDriver..ctor(ICommandExecutor executor, ICapabilities capabilities) in D:\SeleniumHQ\selenium\dotnet\src\webdriver\WebDriver.cs:line 59
   at OpenQA.Selenium.Firefox.FirefoxDriver..ctor(FirefoxDriverService service, FirefoxOptions options, TimeSpan commandTimeout) in D:\SeleniumHQ\selenium\dotnet\src\webdriver\Firefox\FirefoxDriver.cs:line 190
   at OpenQA.Selenium.Firefox.FirefoxDriver..ctor(FirefoxDriverService service) in D:\SeleniumHQ\selenium\dotnet\src\webdriver\Firefox\FirefoxDriver.cs:line 132

Reproducible Code

var service = FirefoxDriverService.CreateDefaultService();

service.LogPath = "E:\\firefox.log";
service.LogLevel = FirefoxDriverLogLevel.Trace;

using var webDriver = new FirefoxDriver(service);

[selenium-ci]

@nvborisenko, thank you for creating this issue. We will troubleshoot it as soon as we can.

Selenium Triage Team: remember to follow the Triage Guide

[diemol]

I could not reproduce this. But maybe this is a Windows thing?

So I went and enabled the tests Titus created a while ago for our docs and executed them on GH Actions on Ubuntu, macOS, and Windows. They all passed.

https://github.com/SeleniumHQ/seleniumhq.github.io/pull/2401/files
https://github.com/SeleniumHQ/seleniumhq.github.io/actions/runs/16649315177?pr=2401

Could you please double check and help me understand how this can be reproduced?

[nvborisenko]

Quickly walked through testing results by the link you provided, and seems these tests are skipped:

Starting test execution, please wait...
  A total of 1 test files matched the specified pattern.
    Skipped DriverLocation
    Skipped LogsToConsole
    Skipped LogsLevel
    Skipped ConfigureDriverLogs
    Skipped LogsToConsole
    Skipped LogsLevel
    Skipped ConfigureDriverLogs
    Skipped LogsToConsole
    Skipped StopsTruncatingLogs
    Skipped SetProfileLocation
    Skipped LogsToFile
    Skipped LogsToConsole
    Skipped BasicOptions
    Skipped EnableLogs
  
  Passed!  - Failed:     0, Passed:   115, Skipped:    14, Total:   129, Duration: 8 m 26 s - SeleniumDocs.dll (net8.0)

[diemol]

They are not. The skipped ones are the ones for Chrome and Edge.

[nvborisenko]

OK, then I need to provide simple reproducible project. Please give me a chance to prepare it.

[nvborisenko]

Abc.zip

Here we go:

• Unpack it
• dotnet run (it automatically restores the nightly package from this folder)

And the error is:

Unhandled exception. OpenQA.Selenium.WebDriverException: Cannot start the driver service on http://localhost:53953/
   at OpenQA.Selenium.DriverService.Start()
   at OpenQA.Selenium.Remote.DriverServiceCommandExecutor.ExecuteAsync(Command commandToExecute)
   at OpenQA.Selenium.WebDriver.ExecuteAsync(String driverCommandToExecute, Dictionary`2 parameters)
   at OpenQA.Selenium.WebDriver.Execute(String driverCommandToExecute, Dictionary`2 parameters)
   at OpenQA.Selenium.WebDriver.StartSession(ICapabilities capabilities)
   at OpenQA.Selenium.WebDriver..ctor(ICommandExecutor executor, ICapabilities capabilities)
   at OpenQA.Selenium.Firefox.FirefoxDriver..ctor(FirefoxDriverService service, FirefoxOptions options, TimeSpan commandTimeout)
   at OpenQA.Selenium.Firefox.FirefoxDriver..ctor(FirefoxDriverService service)
   at Program.<Main>$(String[] args) in E:\Temp\Abc\Program.cs:line 8

PS: I built Selenium.WebDriver.4.35.0-nightly202506301117.nupkg locally, so execute the project if you trust me.