Run the server on your LAN

The server only introduces devices

Each computer stays connected to the server, which is how they find each other and exchange connection details. Once connected, what you copy goes straight between the two computers. Only when that fails does it pass through the server, still encrypted.

• Signaling, TCP 8787. Every computer stays connected to it to find the others, pair and exchange connection details.
• Direct. On a LAN, content almost always goes straight between the two computers, at the speed of your network.
• Relay, UDP 3478. Only used when devices can't reach each other: guest networks, Wi‑Fi with client isolation, separate subnets.

Before you start

A computer that stays on

Windows 10 or 11, macOS 13 or later, or any Linux, including one of the two computers you sync. Sync pauses while it's off or asleep and resumes when it wakes. A NAS, home router or Mac mini is ideal; the server uses about 15 MB of RAM.

A fixed address

Reserve an address for it in your router's DHCP settings (often called DHCP reservation or static lease). Otherwise, when the router hands out a new address, every computer has to be updated.

The same network

Devices just need to be on the same Wi‑Fi or wired network. Guest networks and Wi‑Fi with client (AP) isolation block devices from reaching each other; use another network or turn isolation off.

No sync away from it

The server is only reachable on your LAN, so a laptop taken elsewhere catches up when it's back.

Install the server

Choose the system of the computer that will run the server. The script finds the computer's LAN address, sets the server to start automatically, and prints the address to enter in the apps.

> Stopping the running version
> Installing to C:\Program Files\CopySync Server
> Registering the service CopySyncServer (relay address 192.168.1.20)
> Allowing it through Windows Firewall
> Starting
  √ Running

Installed: copysync-server 1.6.4. It runs as a Windows service and starts with Windows.
In CopySync on each computer, set Settings > Signaling server to:

    ws://192.168.1.20:8787/signal

  Program    C:\Program Files\CopySync Server
  Logs       C:\ProgramData\CopySync Server\server.log
  Restart    Restart-Service CopySyncServer (in an administrator PowerShell)
  Uninstall  double-click uninstall.cmd

% ./install.sh
▶ Stopping the running version
▶ Installing to /Users/me/Library/Application Support/CopySync Server
▶ Writing the LaunchAgent (relay address 192.168.1.20)
▶ Starting
  ✓ Running

Installed: copysync-server 1.6.4. It starts whenever you log in to this Mac.
In CopySync on each computer, set Settings → Signaling server to:

    ws://192.168.1.20:8787/signal

  Logs       /Users/me/Library/Logs/CopySync/server.log
  Restart    launchctl kickstart -k gui/501/com.copysync.server
  Uninstall  ./install.sh uninstall

$ sudo ./install.sh
▶ Installing the binary to /usr/local/bin
▶ Writing the systemd unit
▶ Writing /etc/copysync/server.env (relay address 192.168.1.20)
▶ Starting
  ✓ Running

Installed: copysync-server 1.6.4
In CopySync on each computer, set Settings → Signaling server to:

    ws://192.168.1.20:8787/signal

  Config     /etc/copysync/server.env
  Logs       journalctl -u copysync-server -f
  Restart    systemctl restart copysync-server
  Uninstall  sudo ./install.sh uninstall

Open in your firewall: TCP 8787 (signaling), UDP 3478 (STUN and TURN), UDP 32768-60999 (relay ports, assigned by the OS)

Check that other computers can reach it

On another computer, open http://192.168.1.20:8787/healthz in a browser (with your address). If you see this line, the network path works.

{"status":"ok","version":"1.6.4"}

If it doesn't load, see the questions below.

Enter the address on each computer

1. Open Settings

   Open CopySync on each computer, including the one running the server, and go to Settings.

2. Enter the address

   Under Signaling server, enter ws://192.168.1.20:8787/signal with your address and press Return or Enter.

3. Check the status

   When Connection shows a green Connected, you're set. Pair your devices under Devices and copying starts syncing.

Haven't installed the app yet? See the quick start.

Questions