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Which ports to open in a firewall

Updated

Written for Synergy 3 (v3.8.4) and Synergy 1 (v1.22.3), checked 20 October 2026.

Port numbers

  • Synergy 3: TCP port 24800, plus two extra ports, 24802 and 24804
  • Synergy 1: TCP port 24800

What you can do

On Windows you normally won't need to do anything, because the installer adds Windows Firewall rules for its 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 our app's 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:

  1. On the computer whose keyboard and mouse you share: 
    sudo ufw allow 24800/tcp
  2. On every computer, allow the other ports your product uses:
    • Synergy 3: run both of these, the second so auto discovery can find your other computers: 
      sudo ufw allow 24802/tcp
      sudo ufw allow 5353/udp
    • Synergy 1: nothing more, since it uses only port 24800.

To allow only one other computer, name its address before the port:

sudo ufw allow from 192.168.1.13 to any port 24800 proto tcp

This reads as: allow traffic from 192.168.1.13 (your other computer) to any of this computer's addresses, on port 24800, over TCP. A rule with the port on the other computer's side (192.168.1.13 24800) only matches traffic sent from that port, and both apps 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:

  1. On the computer whose keyboard and mouse you share: 
    sudo firewall-cmd --permanent --add-port=24800/tcp
  2. On every computer, allow the other ports your product uses:
    • Synergy 3: run both of these, the second for auto discovery: 
      sudo firewall-cmd --permanent --add-port=24802/tcp
      sudo firewall-cmd --permanent --add-service=mdns
    • Synergy 1: nothing more, since it uses only port 24800.
  3. 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. The Core process is called "synergy-core".

What Synergy 3's other ports are for is in its section: Synergy 3

How to change the port

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). Where to change it is in your product's section: Synergy 3 or Synergy 1

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.

What follows depends on your product: Synergy 3 or Synergy 1

Synergy 3

The Background Service's ports

Ports 24802 and 24804 are used by the Background Service, 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.

How to change the port

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.

Synergy 1

How to change the port

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.

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