coturn STUN requests work locally, but not for remote connections - webrtc

Question

I've successfully made a TURN request to coturn server (https://github.com/coturn/coturn), but failed when executing a STUN request. If I try to STUN connect to coturn server from the same machine running the server using turnutils_stunclient myIP, the server responds with
RFC 5780 response 1
0: IPv4. Response origin: : IP1:3478
0: IPv4. Other addr: : IP2:3479
0: IPv4. UDP reflexive addr: IP1:36457
========================================
RFC 5780 response 2
0: IPv4. Response origin: : IP2:3479
0: IPv4. Other addr: : IP2:3479
0: IPv4. UDP reflexive addr: IP1:36457
========================================
RFC 5780 response 3
0: IPv4. Response origin: : IP2:3479
0: IPv4. Other addr: : IP2:3479
0: IPv4. UDP reflexive addr: IP1:36458
, which is great! To test STUN requests remotely, I've also installed coturn on my laptop. If I make the same request from my laptop, the stun server responds with only 1 response and hangs after that.
RFC 5780 response 1
0: IPv4. Response origin: : IP1:3478
0: IPv4. Other addr: : IP2:3479
0: IPv4. UDP reflexive addr: IP1:36457
There is no second and third message and the command line is blocked.
The problem is further confirmed when running javascript request:
function checkTURNServer(turnConfig, timeout){
return new Promise(function(resolve, reject){
setTimeout(function(){
if(promiseResolved) return;
resolve(false);
promiseResolved = true;
}, timeout || 5000);
var promiseResolved = false
, myPeerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection //compatibility for firefox and chrome
, pc = new myPeerConnection({iceServers:[turnConfig]})
, noop = function(){};
pc.createDataChannel(""); //create a bogus data channel
pc.createOffer(function(sdp){
if(sdp.sdp.indexOf('typ relay') > -1){ // sometimes sdp contains the ice candidates...
promiseResolved = true;
resolve(true);
}
pc.setLocalDescription(sdp, noop, noop);
}, noop); // create offer and set local description
pc.onicecandidate = function(ice){ //listen for candidate events
if(promiseResolved || !ice || !ice.candidate || !ice.candidate.candidate || !(ice.candidate.candidate.indexOf('typ relay')>-1)) return;
promiseResolved = true;
resolve(true);
};
});
}
checkTURNServer({"url":"stun:IP1:3478"}).then(function(bool){
console.log('is TURN server active? ', bool? 'yes':'no'); // prints no!!
}).catch(console.error.bind(console));
What should I do to make STUN requests work? Can you point me in the right direction?
-----------------Additional info---------------------
I've tested just TURN functionality, and I was able connect:
checkTURNServer({"url":"turn:IP1:3478",username: 'mainuser',
credential: 'mainpassword' }).then(function(bool){
console.log('is TURN server active? ', bool? 'yes':'no'); // prints yes
}).catch(console.error.bind(console));
I've installed coturn and configured it as a service. This is the contents of my /etc/systemd/system/coturn.service file:
[Unit]
Description=turnserver Service
After=network.target
[Service]
Type=simple
User=root
ExecStart=/usr/local/bin/turnserver -c /usr/local/etc/turnserver.conf
Restart=on-abort
[Install]
WantedBy=multi-user.target
When I run systemctl start coturn, service starts normally.
Contents of /usr/local/etc/turnserver.conf
listening-ip=IP1
listening-ip=IP2
lt-cred-mech
user=mainuser:mainpassword
realm=mydomain.com
max-bps=128000
cert=/etc/letsencrypt/live/mydomain.com/cert.pem
pkey=/etc/letsencrypt/live/mydomain.com/privkey.pem
result of iptables -S
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-N FORWARD_IN_ZONES
-N FORWARD_IN_ZONES_SOURCE
-N FORWARD_OUT_ZONES
-N FORWARD_OUT_ZONES_SOURCE
-N FORWARD_direct
-N FWDI_iredmail
-N FWDI_iredmail_allow
-N FWDI_iredmail_deny
-N FWDI_iredmail_log
-N FWDO_iredmail
-N FWDO_iredmail_allow
-N FWDO_iredmail_deny
-N FWDO_iredmail_log
-N INPUT_ZONES
-N INPUT_ZONES_SOURCE
-N INPUT_direct
-N IN_iredmail
-N IN_iredmail_allow
-N IN_iredmail_deny
-N IN_iredmail_log
-N OUTPUT_direct