Life's random bits By b1thunt3r (aka Ishan Jain)…

Solidworks Host File Block Fix May 2026

To fix a SOLIDWORKS "host file block" error, you typically need to map your license server's IP address to its hostname within the Windows hosts file or ensure your antivirus isn't preventing SOLIDWORKS from reading it. Quick Fix: Modifying the Windows Hosts File

If your client machine cannot resolve the server name (DNS issue), you must manually map it to allow a connection to the SOLIDWORKS SolidNetWork License (SNL) Manager.

Run Notepad as Administrator: Click Start, type Notepad, right-click it, and select Run as Administrator.

Open the Hosts File: In Notepad, go to File > Open. Navigate to C:\Windows\System32\drivers\etc\. Change the file type filter in the bottom right from "Text Documents (*.txt)" to All Files.

Add Your Server Entry: At the bottom of the file (on a new line), type the server's IP address, press Tab, and then type the server's name. Example: 192.168.1.100 MyLicenseServer

Save and Flush DNS: Save the file. Then, open a Command Prompt and type ipconfig /flushdns to force Windows to recognize the new mapping. Troubleshooting "Can't Open/Write to Hosts File"

If you receive an error that the hosts file is blocked or cannot be modified, check these settings:

Antivirus Software: Programs like SentinelOne, ZoneAlarm, and Webroot are known to block changes to the hosts file. Look for settings like "Lock Hosts File" or "Prevent modification of HOSTS file" and temporarily disable them.

Read-Only Attribute: Right-click the hosts file, select Properties, and ensure Read-only is unchecked. solidworks host file block fix

Correct Permissions: In file Properties > Security, ensure your user account has Write and Modify permissions. Related Network Blocks

If you still cannot connect after updating the hosts file, the block may be at the firewall level:

Firewall Ports: Ensure TCP ports 25734 and 25735 are open for both Inbound and Outbound rules on both the server and client machines.

SNL Manager Setting: In the SolidNetWork License Manager, ensure the box "A firewall is in use on this server" is checked so it uses a static port for communication.

7) Additional checks if problems persist

  • Check for other blocking mechanisms:
    • Antivirus or endpoint protection quarantines/blocks.
    • Local firewall rules blocking outbound connections.
    • Proxy settings in Internet Options.
  • Reset Winsock (Command Prompt as admin): netsh winsock reset then restart.
  • Confirm system time and date are correct.
  • Temporarily disable VPN and retry activation.
  • If using SolidNetWork License Manager, ensure the client points to the correct license server hostname/IP and that that server is reachable (ping/tracert).

Important Notes

  • Firewall Method: Editing the host file is the "manual" way. For a more robust block, use Windows Defender Firewall with Advanced Security. Create an Outbound Rule to Block the connection for the executable SLDWORKS.exe (usually located in C:\Program Files\SOLIDWORKS Corp\SOLIDWORKS).
  • License Manager: If you are trying to block a specific network license server, replace the domains above with the specific IP address or hostname of your license server.
  • Permissions: If you cannot save the file, ensure you opened Notepad as Administrator. If access is still denied, check the file properties to ensure "Read-only" is unchecked.

SOLIDWORKS Host File Block Fix: A Comprehensive Guide

Are you experiencing issues with SOLIDWORKS due to a blocked host file? Do you see an error message indicating that the software is unable to connect to the license server or access certain features? You're not alone. In this article, we'll explore the SOLIDWORKS host file block fix, a common problem that affects many users. We'll provide a step-by-step guide on how to resolve the issue and get your SOLIDWORKS software up and running smoothly.

What is a Host File?

A host file is a text file used by the operating system to map hostnames to IP addresses. It's a crucial file that helps your computer communicate with other devices on a network. The host file is usually located in the C:\Windows\System32\drivers\etc directory on Windows systems. To fix a SOLIDWORKS "host file block" error,

What Causes a Host File Block in SOLIDWORKS?

When you install SOLIDWORKS, it may create entries in the host file to facilitate communication between the software and the license server. However, sometimes these entries can become corrupted or blocked, causing issues with the software. Here are some common reasons that can lead to a host file block:

  1. Corrupted or incorrect entries: If the entries in the host file are incorrect or corrupted, SOLIDWORKS may not be able to read them properly, leading to a block.
  2. Antivirus software interference: Some antivirus software may flag the host file as a potential threat and block it, causing issues with SOLIDWORKS.
  3. System configuration changes: Changes to the system configuration, such as updates to the network settings or changes to the license server, can cause the host file to become outdated.

Symptoms of a Host File Block

If you're experiencing any of the following symptoms, it's possible that your host file is blocked:

  1. Error messages: You see error messages indicating that SOLIDWORKS is unable to connect to the license server or access certain features.
  2. License server issues: You're experiencing issues with the license server, such as being unable to activate or deactivate licenses.
  3. Feature access issues: You're unable to access certain features or tools within SOLIDWORKS.

SOLIDWORKS Host File Block Fix: Step-by-Step Guide

To fix the host file block, follow these steps:

Method 1: Manually Editing the Host File

  1. Open the host file: Open the host file in a text editor, such as Notepad, with administrator privileges. To do this, right-click on Notepad and select "Run as administrator."
  2. Locate the SOLIDWORKS entries: Look for entries related to SOLIDWORKS, such as 127.0.0.1 localhost or ::1 localhost. These entries may be at the bottom of the file.
  3. Delete the SOLIDWORKS entries: Delete any entries related to SOLIDWORKS.
  4. Save the file: Save the file and close it.

Method 2: Using the SOLIDWORKS License Server Tool Check for other blocking mechanisms:

  1. Download the License Server Tool: Download the SOLIDWORKS License Server Tool from the Dassault Systèmes website.
  2. Run the tool: Run the tool and select the "Fix Hosts File" option.
  3. Follow the prompts: Follow the prompts to fix the host file.

Method 3: Resetting the Host File

  1. Rename the host file: Rename the host file to hosts.old.
  2. Create a new host file: Create a new host file by copying the contents of the hosts.sample file (usually located in the same directory as the host file).
  3. Restart SOLIDWORKS: Restart SOLIDWORKS and see if the issue is resolved.

Additional Troubleshooting Steps

If the above methods don't resolve the issue, try the following:

  1. Check antivirus software: Check your antivirus software settings to ensure that it's not blocking the host file.
  2. Check system configuration: Verify that your system configuration, including network settings and license server settings, is correct.
  3. Contact SOLIDWORKS support: Contact SOLIDWORKS support for further assistance.

Conclusion

Note: This draft assumes the "fix" refers to attempting to block SolidWorks license verification servers via the Windows hosts file to bypass licensing (piracy). I have framed this as a warning against that practice.

Step 3 – Open as Administrator

  • Right-click on Notepad (or any text editor) and select Run as administrator.
  • In Notepad: File → Open → Navigate to C:\Windows\System32\drivers\etc\.
  • Change the file filter from Text Documents (*.txt) to All Files (*.*).
  • Select hosts and click Open.

2. Malware Disguised as "Activators"

Most tutorials for the host file block fix require you to also run a "license activator" or "patch.exe." These executables are common vectors for:

  • Ransomware (encrypts your CAD files)
  • Keyloggers (steals your passwords)
  • Cryptominers (destroys your CPU performance)

Step 2 – Backup the Original

  • Copy the hosts file to your desktop (right-click → Copy, then Paste).
  • Rename the copy to hosts_backup.txt.

8) Reverting changes

  • If problems worsen, restore the backed-up hosts file:
    1. Copy backup to C:\Windows\System32\drivers\etc and overwrite.
    2. Flush DNS and restart as above.

6. How to implement the fix (Correctly)

If you decide to proceed, here is the correct procedure:

  1. Identify the IP: Ping the server name to get the IP, or ask IT for the static IP.
  2. Open Notepad as Admin: Search for Notepad, right-click, "Run as Administrator."
  3. Open the File: File > Open > C:\Windows\System32\drivers\etc\hosts (Change file type from Text Documents to "All Files" to see it).
  4. Add the Entry: At the bottom, type: [IP Address] [Server Name] (Example: 192.168.1.100 SW_LICENSE_SERVER)
  5. Save and Flush DNS: Save the file. Open Command Prompt (Admin) and type ipconfig /flushdns.

9) When to contact SolidWorks support

Contact support or your reseller if:

  • License still fails after removing host entries and checking firewall/AV.
  • The license server is managed by your organization and requires specific host entries.
  • You suspect a corrupted or tampered license file.