I think i found the setup for private network:
nano /etc/spreed/webrtc.conf
turnURIs = turn:MyDnsService:8443?transport=udp
; Shared secret authentication for TURN user generation if the TURN server is
; protected (which it should be).
; See http://tools.ietf.org/html/draft-uberti-behave-turn-rest-00 for details.
; A supported TURN server is https://code.google.com/p/rfc5766-turn-server/.
turnSecret = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
; Enable renegotiation support. Set to true to tell clients that they can
On my router I’ve redirect the port 8443 to my nextcloud/webrtc/coturn server
nano etc/turnserver.conf
listening-port=8443
alt-listening-port=3478
fingerprint
lt-cred-mech
use-auth-secret
static-auth-secret=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
realm=MyDnsService
total-quota=100
bps-capacity=0
stale-nonce
cipher-list="ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AES:RSA+3DES:!ADH:!AECDH:!MD5"
log-file=/var/log/spreed/turn/turn.log
no-loopback-peers
no-multicast-peers
cert=/etc/letsencrypt/XXX/cert.pem
pkey=/etc/letsencrypt/XXX/privkey.pem
I’ve tried between my phone on the 3G , my laptop on the local network and my tablet on a public wifi, connected all together 