Written for Synergy 3 (v3.7.2) and Synergy 1 (v1.21.4), checked 3 October 2026.
Port numbers
Synergy 1 uses TCP port 24800.
Synergy 3 also uses port 24800, but adds two extra ports, 24802 and 24804.
What you can do
On Windows you normally won't need to do anything, because the Synergy 1 and Synergy 3 installers add Windows Firewall rules for their processes. On macOS and Linux, and with a third-party firewall (one that you or your company installed or set up), you may need to allow the Synergy 1 or Synergy 3 processes or the port numbers yourself. Please check the documentation for your firewall if you're not sure how.
How we use the ports
Port 24800 is used by Synergy Core, a common component used by both Synergy 1 and Synergy 3. The Core is the part of our app that does the actual keyboard and mouse sharing. In both Synergy 1 and Synergy 3, the Core process is called "synergy-core".
Ports 24802 and 24804 are used by the Background Service in Synergy 3, which manages auto discovery, config synchronization, and launching of Synergy Core. The process name of the Background Service is "synergy-service". Port 24802 carries config synchronization between computers, and 24804 carries auto discovery.
Note: In case you're wondering, Synergy 3 uses port 24803 on each computer for communication between its window and the Background Service. It only listens locally (127.0.0.1) and isn't used over the network, so you won't need to add it to your firewall. Synergy 1 uses no local ports for this.
How to change the port
In Synergy 1, you can change the port number for the Core process. You may want to do this, for example, if you have a port conflict (e.g. some other app is using 24800 for some reason). Open Preferences (in the Edit menu on Windows and Linux, or the Synergy menu on macOS), go to the Network tab, change Port and click Save.
In Synergy 3, go to Advanced, then Miscellaneous, and change Core server/client port. The setting applies to all of your computers. You can't change the Background Service port numbers from the app.
What is a port?
When your computer receives a message from another computer over the network (in our case the LAN, or local area network), it needs to know which process is expecting the message. That's where ports come in. When a process first uses the network, it "binds" itself to a port number that is also included in the message it sends out so the other computer(s) know which port to send back to. Then, when your computer gets the response, it looks at the port number and passes the message on to the process that's bound to that port.