---
name: "syncthing-networking"
section: "7"
platform: "linux"
package: "syncthing"
version: "2.1.7-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/syncthing-networking"
---

# syncthing-networking(7)

Firewall Setup

## NAME

syncthing-networking - Firewall Setup

## ROUTER SETUP

### Port Forwards

If you have a NAT router which supports UPnP, the easiest way to get a working port forward is to make sure UPnP setting is enabled on both Syncthing and the router – Syncthing will try to handle the rest. If it succeeds you will see a message in the console saying:

```
Created UPnP port mapping for external port XXXXX on UPnP device YYYYY.
```

If this is not possible or desirable, you should set up a port forwarding for ports **22000/TCP** and **22000/UDP** (or whichever port is set in the *Sync Protocol Listen Address* setting). The external forwarded ports and the internal destination ports have to be the same (e.g. 22000/TCP).

Communication in Syncthing works both ways. Therefore if you set up port forwards for one device, other devices will be able to connect to it even when they are behind a NAT network or firewall.

In the absence of port forwarding, *Relaying* may work well enough to get devices connected and synced, but will perform poorly in comparison to a direct connection.

### Local Discovery

The router needs to allow/forward broad-/multicasts for local discovery to work. Usually these are allowed by default in a single local subnet, but may be blocked between different subnets or even between a bridged Wi-Fi and LAN.

If you are unable to set up your router thus or your firewall as shown below, and your devices have static IP addresses, you can specify them directly by changing the default **dynamic** setting for *Addresses* to something like: **tcp://192.168.1.xxx:22000, dynamic**.

## LOCAL FIREWALL

If your PC has a local firewall, you will need to open the following ports for incoming and outgoing traffic:

- •

  Port **22000/TCP**: TCP based sync protocol traffic

- •

  Port **22000/UDP**: QUIC based sync protocol traffic

- •

  Port **21027/UDP**: for discovery broadcasts on IPv4 and multicasts on IPv6

If you configured a custom port in the *Sync Protocol Listen Address* setting, you have to adapt the firewall rules accordingly.

### Uncomplicated Firewall (ufw)

If you’re using **ufw** on Linux and have installed the *Syncthing package* \<**https://apt.syncthing.net/**\>, you can allow the necessary ports by running:

```
sudo ufw allow syncthing
```

If you also want to allow external access to the Syncthing web GUI, run:

```
sudo ufw allow syncthing-gui
```

Allowing external access is **not**  necessary for a typical installation.

You can then verify that the ports mentioned above are allowed:

```
sudo ufw status verbose
```

In case you installed Syncthing manually you can follow the *instructions to manually add the syncthing preset* \<**https://github.com/syncthing/syncthing/tree/main/etc/firewall-ufw**\> to ufw.

### Firewalld

If you are using *Firewalld* \<**https://firewalld.org/**\> it has included support for syncthing (since version 0.5.0, January 2018), and you can enable it with:

```
sudo firewall-cmd --zone=public --add-service=syncthing --permanent
sudo firewall-cmd --reload
```

Similarly there is also a **syncthing-gui** service.

## REMOTE WEB GUI

To be able to access the web GUI from other computers, you need to change the *GUI Listen Address* setting from the default **127.0.0.1:8384** to **0.0.0.0:8384**. You also need to open the port in your local firewall if you have one.

### Tunneling via SSH

If you have SSH access to the machine running Syncthing but would rather not open the web GUI port to the outside world, you can access it through a SSH tunnel instead. You can start a tunnel with a command like the following:

```
ssh -L 9999:localhost:8384 machine
```

This will bind to your local port 9999 and forward all connections from there to port 8384 on the target machine. This still works even if Syncthing is bound to listen on localhost only.

## VIA A PROXY

Syncthing can use a SOCKS5 proxy for outbound connections. Please see *Using Proxies*.

## AUTHOR

The Syncthing Authors

## COPYRIGHT

2014-2026, The Syncthing Authors