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.
Allow the ports on Linux
With ufw, the firewall on Ubuntu, Linux Mint and many other distributions, run these in a terminal:
- On the server (the computer whose keyboard and mouse you share), for Synergy 1 or Synergy 3:
sudo ufw allow 24800/tcp
- On every computer running Synergy 3:
sudo ufw allow 24802/tcp
- On every computer running Synergy 3, so auto discovery can find your other computers:
sudo ufw allow 5353/udp
To allow only one other computer, name its address before the port:
sudo ufw allow from 192.168.1.13 to any port 24802 proto tcp
This reads as: allow traffic from 192.168.1.13 (your other computer) to any of this computer's addresses, on port 24802, over TCP. A rule with the port on the other computer's side (192.168.1.13 24802) only matches traffic sent from that port, and Synergy 1 and Synergy 3 connect from a random one, so put the port after to any port.
With firewalld, the firewall on Fedora, Red Hat Enterprise Linux and openSUSE:
- On the server, for Synergy 1 or Synergy 3:
sudo firewall-cmd --permanent --add-port=24800/tcp
- On every computer running Synergy 3:
sudo firewall-cmd --permanent --add-port=24802/tcp
- On every computer running Synergy 3, for auto discovery:
sudo firewall-cmd --permanent --add-service=mdns
- Load the new rules:
sudo firewall-cmd --reload
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. Auto discovery finds your other computers with multicast DNS, on UDP port 5353, and announces the port number 24804.
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.