Scroll to the very bottom of the file. Start a new line beneath any existing text. Enter the local loopback IP address ( 127.0.0.1 ), press the Tab key, and enter the target licensing domain.

The Windows hosts file is a plain text file that maps hostnames to IP addresses. It is used to override DNS settings. Sometimes, security software, network policies, or previous installations of unauthorized software can add entries to this file that intentionally block access to specific websites—in this case, SolidWorks activation servers. When this happens, you might see errors like: "Cannot connect to the server" "License activation failed"

Highlight these lines and delete them. Ensure there are no leading # symbols on lines you want the system to read (though in this case, you want the system to reach these servers, so the lines shouldn't exist at all). 3. Save and Flush DNS Go to File > Save in Notepad. Open the Command Prompt (type cmd in the Start menu).

The default port used for the SolidNetWork License Manager daemon.

If the host file fix does not work, consider these other common "blocks": Firewall Ports: TCP ports 25734 and 25735

SolidWorks relies on a licensing system that frequently communicates with validation servers. If your workstation cannot reach these servers, or if a corrupt local network configuration blocks the connection, the software will trigger validation errors, license expiration warnings, or refuse to launch entirely.

Disclaimer: This guide is intended for resolving issues on legally licensed installations of SolidWorks. Modifying the hosts file to bypass licensing mechanisms is against the terms of service.

Before you rush to edit system files, ensure you actually have the Hosts file block issue. Many users misdiagnose a simple firewall rule or expired subscription.

Open the from your Windows Start Menu. Navigate to the Server List tab.

Before applying a fix, determine if your host file is actually the source of the problem. Common symptoms include: