1SYNCTHING-NETWORKING(7) Syncthing SYNCTHING-NETWORKING(7)
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6 syncthing-networking - Firewall Setup
7
9 Port Forwards
10 If you have a NAT router which supports UPnP, the easiest way to get a
11 working port forward is to make sure UPnP setting is enabled on both
12 Syncthing and the router – Syncthing will try to handle the rest. If it
13 succeeds you will see a message in the console saying:
14 Created UPnP port mapping for external port XXXXX on UPnP device YYYYY.
16 If this is not possible or desirable, you should set up a port forward‐
18 ing for ports 22000/TCP and 22000/UDP (or whichever port is set in the
19 Sync Protocol Listen Address setting). The external forwarded ports
20 and the internal destination ports have to be the same (e.g.
21 22000/TCP).
22 Communication in Syncthing works both ways. Therefore if you set up
24 port forwards for one device, other devices will be able to connect to
25 it even when they are behind a NAT network or firewall.
26 In the absence of port forwarding, relaying may work well enough to get
28 devices connected and synced, but will perform poorly in comparison to
29 a direct connection.
30 Local Discovery
32 The router needs to allow/forward broad-/multicasts for local discovery
33 to work. Usually these are allowed by default in a single local sub‐
34 net, but may be blocked between different subnets or even between a
35 bridged Wi-Fi and LAN.
36 If you are unable to set up your router thus or your firewall as shown
38 below, and your devices have static IP addresses, you can specify them
39 directly by changing the default dynamic setting for Addresses to some‐
40 thing like: tcp://192.168.1.xxx:22000, dynamic.
41
43 If your PC has a local firewall, you will need to open the following
44 ports for incoming and outgoing traffic:
45 • Port 22000/TCP: TCP based sync protocol traffic
47 • Port 22000/UDP: QUIC based sync protocol traffic
49 • Port 21027/UDP: for discovery broadcasts on IPv4 and multicasts on
51 IPv6
52 If you configured a custom port in the Sync Protocol Listen Address
54 setting, you have to adapt the firewall rules accordingly.
55 Uncomplicated Firewall (ufw)
57 If you’re using ufw on Linux and have installed the Syncthing package
58 <https://apt.syncthing.net/>, you can allow the necessary ports by run‐
59 ning:
60 sudo ufw allow syncthing
62 If you also want to allow external access to the Syncthing web GUI,
64 run:
65 sudo ufw allow syncthing-gui
67 Allowing external access is not necessary for a typical installation.
69 You can then verify that the ports mentioned above are allowed:
71 sudo ufw status verbose
73 In case you installed Syncthing manually you can follow the
75 instructions to manually add the syncthing preset
76 <https://github.com/syncthing/syncthing/tree/main/etc/firewall-ufw> to
77 ufw.
78 Firewalld
80 If you are using Firewalld <https://www.firewalld.org/> it has included
81 support for syncthing (since version 0.5.0, January 2018), and you can
82 enable it with:
83 sudo firewall-cmd --zone=public --add-service=syncthing --permanent
85 sudo firewall-cmd --reload
86 Similarly there is also a syncthing-gui service.
88
90 To be able to access the web GUI from other computers, you need to
91 change the GUI Listen Address setting from the default 127.0.0.1:8384
92 to 0.0.0.0:8384. You also need to open the port in your local firewall
93 if you have one.
94 Tunneling via SSH
96 If you have SSH access to the machine running Syncthing but would
97 rather not open the web GUI port to the outside world, you can access
98 it through a SSH tunnel instead. You can start a tunnel with a command
99 like the following:
100 ssh -L 9999:localhost:8384 machine
102 This will bind to your local port 9999 and forward all connections from
104 there to port 8384 on the target machine. This still works even if
105 Syncthing is bound to listen on localhost only.
106
108 Syncthing can use a SOCKS5 proxy for outbound connections. Please see
109 proxying.
110
112 The Syncthing Authors
113
115 2014-2019, The Syncthing Authors
116v1 Oct 17, 2021 SYNCTHING-NETWORKING(7)