1STRELAYSRV(1)                      Syncthing                     STRELAYSRV(1)
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NAME

6       strelaysrv - Syncthing Relay Server
7

SYNOPSIS

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>]
14

DESCRIPTION

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/.
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OPTIONS

22       -debug Enable debug output.
23
24       -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
29       -global-rate=<bytes/s>
30              Global rate limit, in bytes/s.
31
32       -keys=<dir>
33              Directory where cert.pem and key.pem is stored (default “.”).
34
35       -listen=<listen addr>
36              Protocol listen address (default “:22067”).
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38       -message-timeout=<duration>
39              Maximum amount of time we wait for relevant messages  to  arrive
40              (default 1m0s).
41
42       -nat   Use UPnP/NAT-PMP to acquire external port mapping
43
44       -nat-lease=<duration>
45              NAT lease length in minutes (default 60)
46
47       -nat-renewal=<duration>
48              NAT renewal frequency in minutes (default 30)
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50       -nat-timeout=<duration>
51              NAT discovery timeout in seconds (default 10)
52
53       -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
60       -per-session-rate=<bytes/s>
61              Per session rate limit, in bytes/s.
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63       -ping-interval=<duration>
64              How often pings are sent (default 1m0s).
65
66       -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
71       -protocol=<string>
72              Protocol used for listening. ‘tcp’ for IPv4 and IPv6, ‘tcp4’ for
73              IPv4, ‘tcp6’ for IPv6 (default “tcp”).
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75       -provided-by=<string>
76              An optional description about who provides the relay.
77
78       -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 transferred, number of clients, etc.)
82
83   Installing
84       Go  to  releases  <https://github.com/syncthing/relaysrv/releases>  and
85       download  the  file appropriate for your operating system. Unpacking it
86       will yield a binary  called  relaysrv  (or  relaysrv.exe  on  Windows).
87       Start this in whatever way you are most comfortable with; double click‐
88       ing should work in any graphical environment. At first start,  relaysrv
89       will  generate  certificate files and database in the current directory
90       unless given flags to the contrary. It will also join the default pools
91       of  relays,  which means that it is publicly visible and any client can
92       connect to it.  The startup  message  prints  instructions  on  how  to
93       change this.
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95       The  relay  server  can also be obtained through apt, the Debian/Ubuntu
96       package manager. Recent releases can be found at syncthing’s apt repos‐
97       itory  <https://apt.syncthing.net/>.  The  name of the package is sync‐
98       thing-relaysrv.
99

SETTING UP

101       Primarily, you need to decide on a directory to store the TLS  key  and
102       certificate  and a listen port. The default listen port of 22067 works,
103       but for optimal compatibility a well known port for  encrypted  traffic
104       such  as  443 is recommended. This may require additional setup to work
105       without running as root or a privileged user, see Running on  port  443
106       as  an  unprivileged user below. In principle something similar to this
107       should work on a Linux/Unix system:
108
109          $ sudo useradd relaysrv
110          $ sudo mkdir /etc/relaysrv
111          $ sudo chown relaysrv /etc/relaysrv
112          $ sudo -u relaysrv /usr/local/bin/relaysrv -keys /etc/relaysrv
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114       This creates a user relaysrv and a directory /etc/relaysrv to store the
115       keys.  The keys are generated on first startup. The relay will join the
116       global relay pool, unless a -pools="" argument is given.
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118       To make the relay server start automatically at boot,  use  the  recom‐
119       mended procedure for your operating system.
120
121   Client configuration
122       Syncthing  can be configured to use specific relay servers (exclusively
123       of the public pool) by adding the required servers to the Sync Protocol
124       Listen Address field, under Actions and Settings. The format is as fol‐
125       lows:
126          relay://<host name|IP>[:port]/?id=<relay device ID>
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128       For example:
129          relay://private-relay-1.exam‐
130          ple.com:443/?id=ITZRNXE-YNROGBZ-HXTH5P7-VK5NYE5-QHRQGE2-7JQ6VNJ-KZUEDIU-5PPR5AM
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132       The relay’s device ID is output on start-up.
133
134   Running on port 443 as an unprivileged user
135       It is recommended that you run the relay on port 443 (or  another  port
136       which  is  commonly  allowed  through corporate firewalls), in order to
137       maximise the chances that people are able to connect. However,  binding
138       to  ports  below  1024 requires root privileges, and running a relay as
139       root is not recommended. Thankfully there are a  couple  of  approaches
140       available to you.
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142       One  option is to run the relay on port 22067, and use an iptables rule
143       to forward traffic from port 443 to port 22067, for example:
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145          iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 443 -j REDIRECT --to-port 22067
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147       Or, if you’re using ufw, add the following to /etc/ufw/before.rules:
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149          *nat
150          :PREROUTING ACCEPT [0:0]
151          :POSTROUTING ACCEPT [0:0]
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153          -A PREROUTING -i eth0 -p tcp --dport 443 -j REDIRECT --to-port 22067
154
155          COMMIT
156
157       You will need to start relaysrv with -ext-address  ":443".  This  tells
158       relaysrv  that  it can be contacted on port 443, even though it is lis‐
159       tening on port 22067. You will also need to let both port 443 and 22067
160       through your firewall.
161
162       Another  option  is  described here <https://wiki.apache.org/httpd/Non
163       RootPortBinding>, although your mileage may vary.
164

FIREWALL CONSIDERATIONS

166       The relay server listens on two ports by default.  One for data connec‐
167       tions    and   the   other   for   providing   public   statistics   at
168       http://relays.syncthing.net/.  The firewall,  such  as  iptables,  must
169       permit incoming TCP connections to the following ports:
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171       · Data  port:   22067/tcp  overridden  with -listen and advertised with
172         -ext-address
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174       · Status port: 22070/tcp overridden with -status-srv
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176       Runtime iptables rules to allow access to the default ports:
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178          iptables -I INPUT -p tcp --dport 22067 -j ACCEPT
179          iptables -I INPUT -p tcp --dport 22070 -j ACCEPT
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181       Please consult Linux distribution  documentation  to  persist  firewall
182       rules.
183

SEE ALSO

185       syncthing-relay(7), syncthing-faq(7), syncthing-networking(7)
186

AUTHOR

188       The Syncthing Authors
189
191       2014-2019, The Syncthing Authors
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196v1                               Feb 17, 2021                    STRELAYSRV(1)
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