1STRELAYSRV(1)                      Syncthing                     STRELAYSRV(1)
2
3
4

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 https://relays.syncthing.net/.
20

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”).
37
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)
49
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.
62
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              https://relays.syncthing.net/endpoint”). Blank  to  disable  an‐
69              nouncement 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”).
74
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 strelaysrv (or strelaysrv.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,  stre‐
89       laysrv  will generate certificate files and database in the current di‐
90       rectory unless given flags to the contrary. It will also join  the  de‐
91       fault  pools of relays, which means that it is publicly visible and any
92       client can connect to it.  The startup message prints  instructions  on
93       how to change this.
94
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 strelaysrv
110          $ sudo mkdir /etc/strelaysrv
111          $ sudo chown strelaysrv /etc/strelaysrv
112          $ sudo -u strelaysrv /usr/local/bin/strelaysrv -keys /etc/strelaysrv
113
114       This creates a user strelaysrv and a directory /etc/strelaysrv to store
115       the  keys. The keys are generated on first startup. The relay will join
116       the global relay pool, unless a -pools="" argument is given.
117
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>
127
128       For example:
129          relay://private-relay-1.example.com:443/?id=ITZRNXE-YN‐
130          ROGBZ-HXTH5P7-VK5NYE5-QHRQGE2-7JQ6VNJ-KZUEDIU-5PPR5AM
131
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.
141
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:
144
145          iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 443 -j REDIRECT --to-port 22067
146
147       Or, if you’re using ufw, add the following to /etc/ufw/before.rules:
148
149          *nat
150          :PREROUTING ACCEPT [0:0]
151          :POSTROUTING ACCEPT [0:0]
152
153          -A PREROUTING -i eth0 -p tcp --dport 443 -j REDIRECT --to-port 22067
154
155          COMMIT
156
157       You  will need to start strelaysrv with -ext-address ":443". This tells
158       strelaysrv 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       https://relays.syncthing.net/.   The  firewall,  such as iptables, must
169       permit incoming TCP connections to the following ports:
170
171       • Data port:  22067/tcp overridden with  -listen  and  advertised  with
172         -ext-address
173
174       • Status port: 22070/tcp overridden with -status-srv
175
176       Runtime iptables rules to allow access to the default ports:
177
178          iptables -I INPUT -p tcp --dport 22067 -j ACCEPT
179          iptables -I INPUT -p tcp --dport 22070 -j ACCEPT
180
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
192
193
194
195
196v1                               Oct 17, 2021                    STRELAYSRV(1)
Impressum