The Sauce Labs Cookbook

Sauce Headless

Front End Performance Testing


External Resources

More Info

Page tree

Versions Compared


  • This line was added.
  • This line was removed.
  • Formatting was changed.

--doctor is a command line utility that you can use to diagnose issues with Sauce Connect Proxy. This topic describes how to read the doctor the log, the errors that --doctor will detect, and how to resolve them. 

Table of Contents

--doctor Diagnostics

When running your Sauce Labs tests with Sauce Connect Proxy, there may be situations in which Sauce Connect Proxy doesn't perform as expected. To make sure everything 's in is in working order, you can run Sauce Connect diagnostic tests by adding appending the --doctor flag to your command-line. 

NOTE: While the --doctor flag to your Sauce Connect command line, like socan facilitate debugging, you'll find most valuable troubleshooting information in your verbose logs (which you'd need to enable), as described in Sauce Connect Proxy Troubleshooting.

See the following sections for more information:

Table of Contents

Running Tests Using the --doctor Flag as a Diagnostics Tool

To use the --doctor flag, you would run the same command for starting the Sauce Connect Proxy, including any additional flags related to your specific tunnel (e.g., --tunnelidentifier or -x to specify a data center). 

NOTE: When adding the --doctor flag to your code, placement matters. Here's the correct order of flags:

sc -u [Your Sauce Username] -k [Your Sauce Access Key] --doctor

Diagnostics Performed

--doctor will  will run a series of diagnostic operations to verify the following:


  • Which DNS servers and SSL certificates can be found in your network when Sauce Connect Proxy boots up



  • Sauce Connect Proxy


  • outbound connections to:

    • on port 443 for the REST API and the primary tunnel connection to the Sauce Labs cloud

    • and on port 443 using the SSL certificates found in your network



  • Connectivity to these Sauce Labs REST API calls:




    • Your Sauce Username]/tunnels


NOTE: Sauce Connect will exit after these checks are performed. A tunnel will not be started.

Identifying and Resolving Common Errors with the --doctor Flag

In the table below, you'll find descriptions of the errors that --doctor will detect and how to resolve them. 


failed to fetch PAC file

...: ...


Indicates the specified PAC file couldn't be downloaded. This may be caused by an incorrect URL, or a network mis-configuration. To troubleshoot this type of issue, try to download the PAC file manually from the machine running Sauce Connect with 


cURL or another HTTP client.

To debug the PAC file you can create one locally and pass it to Sauce Connect Proxy using the --pac option like this:

Code Block
$ sc --pac file:///path/to/pacfile.js

In Windows, remember to add the drive to the path like this:

Code Block
$ sc --pac file://C:/path/to/pacfile.js

failed to fetch or empty PAC file


The connection
Connection to the remote server was
successful, but the PAC file was empty or missing.

both --proxy and --pac are used

Using both may work, but this is unsupported by Sauce Labs and should only be used if directed by the
Sauce Labs support.

invalid REST URL


URL specified in the -x option is invalid.

failed to find proxy via PAC for



PAC file was downloaded successfully, but no proxy was found for this host. This may be the result of an incorrect PAC file: make sure a proxy is specified for all the hosts.

can't resolve ''/... tunnel hostname(s) via any DNS server

Please check your firewall and DNS settings.

To troubleshoot this issue, use dig or host to resolve the domain and verify it is correct:

Code Block
$ dig

your hosts file contains an entry for

...The DNS server can


If this error occurred, it is likely that your DNS server couldn't resolve correctly

, this

. As a result, Sauce Labs Support might have directed someone at your organization to add the host to /etc/hosts. This is most likely because the DNS system has a special configuration for some hosts.

We strongly recommend you

Please remove this entry from the host file: it's usually /etc/hosts on Unix-like systems. With Linux/Mac OS X systems, you can check the hosts file with this command.

Code Block
$ grep '' /etc/hosts

connecting via <proxy> to http://<url>: <error> or connecting to http://<url>: <error>


URL isn't accessible. If you see this error after other errors in the logs, try to fix the previous errors first.

Please refer to the libcurl errors manual to troubleshoot this issue.

SSL connect failed, socket: .


<code_number> code: %d

Secure connection couldn't be established. Please refer to the OpenSSL manual to get more information about the error.

failed to retrieve certificate chain

Some X509 certificates couldn't be imported into the SSL library. This may indicate an issue
with DNS, or public
CAs being unreachable.

failed to reach https?://

Sauce Connect client can't reach
, this
. This indicates that the client doesn't have full Internet connectivity. It may not be an issue
; Sauce Connect only needs access to and its tunnels.

Additional Support

If you need more help, please get in touch with our support team at

To better assist you, when creating your support ticket, please include the following information with your request:





  • --doctor flag
  • Link to your Sauce Labs test from the Test Results page in Sauce Labs, showing reproduction of the problem
  • Your Sauce Connect verbose log, which you can get by adding the -v and -l sc.log options to your Sauce Connect Proxy command line:

sc -u [Your Sauce Username] -k [Your Sauce Access Key] -v -l sc.log

Then, attach the resulting sc.log file to your support request.

More Information