What is TURN?
TURN stands for Traversal Using Relays around NAT. Similar as STUN, it is a network protocol / packet format (IETF RFC 5766) used to assist in the discovery of paths between peers on the Internet. It differs from STUN in that it uses a public relay to transfer packets between peers. TURN is used to exchange media packets when no other option is available. So that it consumes server resources and has an increased latency due to the extra hop in peer to peer connection.
The time when you must use TURN is when one of the peers is behind a symmetric NAT and the other is behind either a symmetric NAT or port-restricted NAT. The frequency of cases where a relay is necessary is around %10 of the overall connections, since STUN is enough for most cases.
Install coTURN Server
Audio / Video based services requires a wide range of UDP ports to be available for WebRTC. In some network restricted sites, such as those behind NAT or a firewall that restricts outgoing UDP connections, users may be unable to make outgoing UDP connections to your media server.
TURN protocol is designed to allow UDP communication flows to bypass NAT or firewalls by forcing the client to connect to the TURN server, and then force TURN server to connect to the destination on their behalf.
Using a TURN server under your control improves the success of connections to your multimedia application and also improves user privacy, since it acts like a proxy so that peers will no longer be sending their IP address information to a public STUN server.
TURN protocol is not really CPU or memory intensive. Additionally, since it’s only used during connection setup (for STUN) and as a fallback for users who would otherwise be unable to connect, the bandwidth requirements aren’t particularly high. For a moderate number of connections, a single small VPS configuration is usually enough. Here you can find my reccomendations to install coTURN:
- At least two vCPUs
- 4GB Memory.
- 20GB HDD. SSD can be used, but not mandatory.
- The most important thing is the networking performance.
- Low jitter (less than 30ms)
- Low latency (less than 150ms)
- Enough bandwidth to handle relayed media streams in both directions.
Having the server behind NAT (like on Amazon EC2) is OK, but all incoming UDP and TCP connections on any port (TCP 80 & 443, UDP 3478, 10000-20000) must be forwarded to coTURN server and not firewalled.
I recommend using a minimal server installation of Debian with netinst or Ubuntu. Since coTURN software uses port TCP 443, the server which coTURN will be installed cannot have any other web applications running.
coTURN is already available in the Debian and Ubuntu repositories and it can be installed with apt-get:
$ sudo apt-get update $ sudo apt-get install coturn
Please note that coTURN will not start automatically until the configuration is finished. You can find the configuration tasks in below.
DNS Entry For coTURN
You need to setup a fully qualified domain name (FQDN) that resolves the external IP address of your coTURN server. You’ll use this domain name to generate a TLS certificate.
Generating TLS Certificates
You can use
certbot to generate free TLS certificates from Let’s Encrypt. To setup
certbot, enter the following commands on your coTURN server:
$ sudo add-apt-repository ppa:certbot/certbot $ sudo apt-get update $ sudo apt-get install certbot
Note: If you face with add-apt-repository command not found error, please use sudo apt-get install software-properties-common command to install the necessary packets.
You can then run a
certbot command like the following to generate the certificate, replacing
turn.fatiherikci.com with the domain name of your TURN server:
$ sudo certbot certonly --standalone --preferred-challenges http \ --deploy-hook "systemctl restart coturn" \ -d turn.fatiherikci.com
Current versions of the certbot command set up automatic renewal by default. Note that when certbot renews the certificate, it will restart coTURN service, so coTURN will start to use the updated certificate files. This will cause an interruption on any ongoing TURN connections. You may change the certbot renewal schedule or disable automatic renewal if you like.
coTURN configuration is stored in
/etc/turnserver.conf file. There are a lot of options and all of them are documented in comments in that file. I include a sample configuration below with comments as the recommended settings, also with notes in places where customization is needed.
You can replace the contents
/etc/turnserver.conf with the file below and make these changes:
turn.fatiherikci.comwith the hostname of your TURN server
- Change the values in bold with your choices.
You can see an example config file below:
server-name=turn.fatiherikci.com realm=turn.fatiherikci.com cert=/etc/letsencrypt/live/turn.fatiherikci.com/cert.pem pkey=/etc/letsencrypt/live/turn.fatiherikci.com/privkey.pem fingerprint listening-ip=0.0.0.0 external-ip= 126.96.36.199/192.168.0.1 #or just write the external ip listening-port=3478 min-port=10000 max-port=20000 log-file=/var/log/turnserver.log verbose lt-cred-mech user=myusername:mypassword
You can now start the COTURN service with this command:
$ systemctl start coturn
Running coTURN as a Service
The Debian / Ubuntu package for coTURN requires that you edit a file to enable at startup. Edit
/etc/default/coturn file and uncomment the following line:
That’s it! coTURN install is complete. Now you have an up and runnning TURN server!
Testing Your TURN Server
To test your coTURN server, you can use Trickle-Ice testing tool. Go to trickle-ice webpage and enter following:
STUN or TURN URI : turn:Your Public IP Address:3478 TURN username: Username TURN password: Password
Then click Add Server button and then click Gather Candidates button. If everything works well, you should see Done as final result.