How to resolve the error "Failed to connect to token.gurobi.com port 443"?

Gurobi's WLS license requires direct HTTPS connections (port 443) to https://token.gurobi.com. If you encounter the "Failed to connect to token.gurobi.com port 443" error, your machine has trouble connecting to Gurobi’s license server. This is often due to an internet connection or network issue, such as firewall or proxy restrictions blocking the connection to the required URLs: https://license.gurobi.com and https://token.gurobi.com.

Check for connectivity issues

1. Check internet connection:
   • Ensure that your computer is connected to the internet. Gurobi's WLS license requires an active internet connection to communicate with the license server.
2. Check access to the required URLs: 
   • Try accessing the URLs in a browser:
     • Open a browser on your computer and go to:
       • https://license.gurobi.com
       • https://token.gurobi.com
     • If either link doesn’t load, something on your network (such as a firewall or security setting) might be blocking the connection.
   • Use Telnet to check port 443:
     • Try using telnet to check if port 443 is open:
       • In the Command Prompt or Terminal, type telnet token.gurobi.com 443 and press Enter.
       • If the screen goes blank or displays a connection message, it means the port is open. If you see an error like “Could not open connection,” the port might be blocked by a firewall.
     • Note: On Windows, you may need to enable Telnet first. To do this, search for “Turn Windows features on or off” in the Start menu and check the box for Telnet Client.

Troubleshooting steps

If the URLs https://license.gurobi.com and https://token.gurobi.com or port 443 are blocked:

1. Request URL Whitelisting
   • Please ask your company or university IT department to whitelist the URLs https://license.gurobi.com and https://token.gurobi.com.
2. Check for Proxy Settings
   • Some networks use a “proxy” that could block the connection. If your company or university network uses a proxy, please set the environment variable HTTPS_PROXY (which defines the proxy address for HTTPS connections) in one of the following ways:  
     • HTTPS_PROXY=http://<proxy-address>:<port>
     • HTTPS_PROXY=http://<username>:<password>@<proxy-address>:<port>
3. Check for Firewalls or Security Restrictions
   • On networks with strict security, firewall settings may be blocking access. Please contact your IT department to confirm if firewall settings prevent connection to the required URLs.
   • Ensure the firewall settings allow communication to the domain name (token.gurobi.com). It is not recommended to resolve the IP address of token.gurobi.com and whitelist only the IP address(es). We provide multiple servers for redundancy reasons so that the IP addresses might change anytime.

Further information

• What URLs are needed to run the Web Licensing Service (WLS)?
• Incident response for errors related to WLS (Web License Service)