simplex-chat/docs/WEBRTC.md

Using custom WebRTC ICE servers in SimpleX Chat

Deploy STUN/TURN server

For this guide, we'll be using the most featureful and battle-tested STUN/TURN server implementation – coturn and Ubuntu 20.04 LTS Linux distribution.

0. Obtain stun.$YOUR_DOMAIN and turn.$YOUR_DOMAIN certificates.

   We're using Let's Encrypt.

1. Install coturn package from the main repository.

apt update && apt install coturn`

2. Uncomment TURNSERVER_ENABLED=1 from /etc/default/coturn:

sed -i '/TURN/s/^#//g' /etc/default/coturn

3. Configure coturn in /etc/turnserver.conf:

   Also, please see comments for each individual option.

# Also listen to 443 port for tls
alt-tls-listening-port=443
# Use fingerprints in the TURN messages
fingerprint
# Use long-term credentials mechanism
lt-cred-mech
# Your credentials
user=$YOUR_LOGIN:$YOUR_PASSWORD
# Your server domain
server-name=$YOUR_DOMAIN
# The default realm to be used for the users when no explicit origin/realm relationship was found
realm=$YOUR_DOMAIN
# Path to your certificates. Make sure they're readable by cotun process user/group
cert=/var/lib/turn/cert.pem
pkey=/var/lib/turn/key.pem
# Use 2066 bits predefined DH TLS key
dh2066
# Log to journalctl
syslog
# User/group which will be running coturn service
proc-user=turnserver
proc-group=turnserver
# Disable weak encryption
no-tlsv1
no-tlsv1_1
no-tlsv1_2

4. Start and enable coturn service:

systemctl enable coturn && systemctl start coturn

5. Optionally, if using ufw firewall, open relevant ports:

• 3478 – "plain" TURN/STUN;
• 5349 – TURN/STUN over TLS;
• 443 – TURN/STUN over TLS, which can bypass firewalls;
• 49152:65535 – port range that Coturn will use by default for TURN relay.

ufw allow 3478 && \
ufw allow 443 && \
ufw allow 5349 && \
ufw allow 49152:65535/tcp && \
ufw allow 49152:65535/udp

Configure mobile apps

To configure your mobile app to use your server:

1. Open Settings / Network & Servers / WebRTC ICE servers and switch toggle Configure ICE servers.

2. Enter all server addresses in the field, one per line, for example if you servers are on the port 5349:

stun:stun.example.com:5349
turn:username:password@turn.example.com:5349

This is it - you now can make audio and video calls via your own server, without sharing any data with our servers (other than the key excange with your contact in E2E encrypted messages).