When Barrier stops passing keyboard and mouse input between computers, the issue usually stems from a network discovery failure, a mismatched server address, or an active firewall blocking the UDP port. Verify that both machines are on the same subnet, ensure the server IP is correct in the client configuration, and check that no security software is intercepting the local network traffic.
Verify Network Connectivity and Subnet
The most common reason for input sharing to fail silently is that the client cannot reach the server machine. Barrier relies on local network communication, typically using UDP ports 24800 and 24801. If the devices are on different subnets or VLANs, the broadcast packets required for auto-discovery will not cross the boundary. First, confirm that both computers are connected to the same router or switch. You can test this by opening a command prompt or terminal on the client machine and pinging the server's IP address. A successful ping indicates basic connectivity, but it does not guarantee that Barrier-specific ports are open. If you are using Wi-Fi, ensure that "Client Isolation" or "AP Isolation" is disabled on your wireless router. This feature is designed to prevent devices on the same Wi-Fi network from communicating with each other for security reasons, which directly conflicts with how Barrier operates. Wired connections are generally more stable for this type of low-latency input sharing. Multi-Staff: Mouse Cursor Losing Focus/Keyboard Dropping Typing discusses similar focus issues that can arise when network latency introduces delays in input transmission. While that article focuses on OS-level focus problems, high latency due to poor network configuration can mimic these symptoms.Check Firewall and Security Software
Even if the network is connected, local firewalls often block the specific ports Barrier uses. Windows Defender Firewall, macOS Application Firewall, and third-party antivirus suites may flag Barrier as an unknown application attempting to access the network. On Windows, navigate to the Windows Security settings and select "Firewall & network protection." Ensure that Barrier is listed under allowed apps. If it is not present, you may need to manually create an inbound rule for UDP ports 24800 and 24801. Similarly, on macOS, go to System Preferences, then Security & Privacy, and look for a notification about Barrier requesting permission to accept incoming connections. Grant this permission if prompted. Third-party security software such as Norton, McAfee, or Kaspersky often has its own network shielding features. These programs might block the broadcast discovery mechanism even if the main firewall allows general internet traffic. Temporarily disabling these shields during setup can help identify if they are the culprit. Remember to re-enable them after confirming the connection works.Configure Server and Client Correctly
Barrier requires one computer to act as the server (the one with the physical keyboard and mouse) and the other(s) to act as clients. The server must be running the Barrier service before the client attempts to connect. In the server interface, note the IP address displayed. It is crucial to use this exact IP address when configuring the client. Do not rely on hostname resolution unless you are certain that DNS or mDNS is functioning correctly on your network. Some users find that using the IP address directly resolves intermittent connection drops caused by DNS caching issues. On the client side, enter the server's IP address into the configuration field. Select the correct screen position relative to the server display. For example, if the client monitor is to the right of the server monitor, set the client screen to the right. Incorrect positioning can cause the cursor to disappear off-screen when moving between displays, making it appear as though the input is not working. Problems with Keyboard and Mouse provides additional context on input handling quirks that may persist even after network issues are resolved, such as modifier key state mismatches.Restart Services and Check Logs
If the above steps do not resolve the issue, restart the Barrier application on both machines. Sometimes, background processes hang or lose their socket bindings. On Windows, you can also use the Task Manager to end any lingeringBarrier.exe processes before relaunching.
Check the application logs for error messages. Barrier typically outputs log information to the console window when launched from the command line or terminal. Look for lines indicating "Connection refused," "Timeout," or "Authentication failed." These messages provide specific clues about where the handshake is breaking down.
For advanced troubleshooting, verify that no other application is using the same UDP ports. Although rare, another piece of software might conflict with Barrier’s port usage. Using a tool like netstat can help identify if port 24800 is already in use by another process.