1STRELAYSRV(1) Syncthing STRELAYSRV(1)
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6 strelaysrv - Syncthing Relay Server
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9 strelaysrv [-debug] [-ext-address=<address>] [-global-rate=<bytes/s>] [-keys=<dir>] [-listen=<listen addr>]
10 [-message-timeout=<duration>] [-nat] [-nat-lease=<duration> [-nat-renewal=<duration>]
11 [-nat-timeout=<duration>] [-network-timeout=<duration>] [-per-session-rate=<bytes/s>]
12 [-ping-interval=<duration>] [-pools=<pool addresses>] [-protocol=<string>] [-provided-by=<string>]
13 [-status-srv=<listen addr>]
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16 Syncthing relies on a network of community-contributed relay servers.
17 Anyone can run a relay server, and it will automatically join the relay
18 pool and be available to Syncthing users. The current list of relays
19 can be found at http://relays.syncthing.net/.
20
22 -debug Enable debug output.
23 -ext-address=<address>
25 An optional address to advertising as being available on. Allows
26 listening on an unprivileged port with port forwarding from e.g.
27 443, and be connected to on port 443.
28 -global-rate=<bytes/s>
30 Global rate limit, in bytes/s.
31 -keys=<dir>
33 Directory where cert.pem and key.pem is stored (default “.”).
34 -listen=<listen addr>
36 Protocol listen address (default “:22067”).
37 -message-timeout=<duration>
39 Maximum amount of time we wait for relevant messages to arrive
40 (default 1m0s).
41 -nat Use UPnP/NAT-PMP to acquire external port mapping
43 -nat-lease=<duration>
45 NAT lease length in minutes (default 60)
46 -nat-renewal=<duration>
48 NAT renewal frequency in minutes (default 30)
49 -nat-timeout=<duration>
51 NAT discovery timeout in seconds (default 10)
52 -network-timeout=<duration>
54 Timeout for network operations between the client and the relay.
55 If no data is received between the client and the relay in this
56 period of time, the connection is terminated. Furthermore, if no
57 data is sent between either clients being relayed within this
58 period of time, the session is also terminated. (default 2m0s)
59 -per-session-rate=<bytes/s>
61 Per session rate limit, in bytes/s.
62 -ping-interval=<duration>
64 How often pings are sent (default 1m0s).
65 -pools=<pool addresses>
67 Comma separated list of relay pool addresses to join (default “‐
68 http://relays.syncthing.net/endpoint”). Blank to disable
69 announcement to a pool, thereby remaining a private relay.
70 -protocol=<string>
72 Protocol used for listening. ‘tcp’ for IPv4 and IPv6, ‘tcp4’ for
73 IPv4, ‘tcp6’ for IPv6 (default “tcp”).
74 -provided-by=<string>
76 An optional description about who provides the relay.
77 -status-srv=<listen addr>
79 Listen address for status service (blank to disable) (default
80 “:22070”). Status service is used by the relay pool server UI
81 for displaying stats (data transfered, number of clients, etc.)
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84 Primarily, you need to decide on a directory to store the TLS key and
85 certificate and a listen port. The default listen port of 22067 works,
86 but for optimal compatibility a well known port for encrypted traffic
87 such as 443 is recommended. This may require additional setup to work
88 without running as root or a privileged user, see Running on port 443
89 as an unprivileged user below. In principle something similar to this
90 should work on a Linux/Unix system:
91 $ sudo useradd relaysrv
93 $ sudo mkdir /etc/relaysrv
94 $ sudo chown relaysrv /etc/relaysrv
95 $ sudo -u relaysrv /usr/local/bin/relaysrv -keys /etc/relaysrv
96 This creates a user relaysrv and a directory /etc/relaysrv to store the
98 keys. The keys are generated on first startup. The relay will join the
99 global relay pool, unless a -pools="" argument is given.
100 To make the relay server start automatically at boot, use the recom‐
102 mended procedure for your operating system.
103 Client configuration
105 Syncthing can be configured to use specific relay servers (exclusively
106 of the public pool) by adding the required servers to the Sync Protocol
107 Listen Address field, under Actions and Settings. The format is as fol‐
108 lows:
109 relay://<host name|IP>[:port]/?id=<relay device ID>
110 For example:
112 relay://private-relay-1.exam‐
113 ple.com:443/?id=ITZRNXE-YNROGBZ-HXTH5P7-VK5NYE5-QHRQGE2-7JQ6VNJ-KZUEDIU-5PPR5AM
114 The relay’s device ID is output on start-up.
116 Running on port 443 as an unprivileged user
118 It is recommended that you run the relay on port 443 (or another port
119 which is commonly allowed through corporate firewalls), in order to
120 maximise the chances that people are able to connect. However, binding
121 to ports below 1024 requires root privileges, and running a relay as
122 root is not recommended. Thankfully there are a couple of approaches
123 available to you.
124 One option is to run the relay on port 22067, and use an iptables rule
126 to forward traffic from port 443 to port 22067, for example:
127 iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 443 -j REDIRECT --to-port 22067
129 Or, if you’re using ufw, add the following to /etc/ufw/before.rules:
131 *nat
133 :PREROUTING ACCEPT [0:0]
134 :POSTROUTING ACCEPT [0:0]
135 -A PREROUTING -i eth0 -p tcp --dport 443 -j REDIRECT --to-port 22067
137 COMMIT
139 You will need to start relaysrv with -ext-address ":443". This tells
141 relaysrv that it can be contacted on port 443, even though it is lis‐
142 tening on port 22067. You will also need to let both port 443 and 22067
143 through your firewall.
144 Another option is described here <https://wiki.apache.org/httpd/Non‐
146 RootPortBinding>, although your mileage may vary.
147
149 The relay server listens on two ports by default. One for data connec‐
150 tions and the other for providing public statistics at
151 http://relays.syncthing.net/. The firewall, such as iptables, must
152 permit incoming TCP connections to the following ports:
153 · Data port: 22067/tcp overridden with -listen and advertised with
155 -ext-address
156 · Status port: 22070/tcp overridden with -status-srv
158 Runtime iptables rules to allow access to the default ports:
160 iptables -I INPUT -p tcp --dport 22067 -j ACCEPT
162 iptables -I INPUT -p tcp --dport 22070 -j ACCEPT
163 Please consult Linux distribution documentation to persist firewall
165 rules.
166
168 syncthing-relay(7), syncthing-faq(7), syncthing-networking(7)
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171 The Syncthing Authors
172
174 2014-2019, The Syncthing Authors
175v1 Mar 17, 2020 STRELAYSRV(1)