A relay server is used to relay communication between Offset nodes. We use relays because most user devices are behind NATs, and therefore do not own a public address. As a result, it is usually very difficult for two user devices to communicate directly.

Recommended prior reading:

Running your own relay

To set up a relay, run:

# Public facing relay address

# Public facing relay port

# Create a directory for the relay's data
mkdir relay

# Generate a new identity for the relay
stmgr gen-ident --output relay/relay.ident

# Generate relay ticket
stmgr relay-ticket \
        --address $RELAY_ADDRESS:$RELAY_PORT \
        --idfile relay/relay.ident \
        --output relay/relay.relay

# Start the relay:
strelay --idfile relay/relay.ident --laddr$RELAY_PORT &

Relay commands explained

We first set RELAY_ADDRESS as a public facing address for the relay. RELAY_ADDRESS is the public facing address of the relays. Nodes will connect to the relay through this address.

If the scope of your experiment is your local machine, you can use If you are running a test at home that includes your mobile phone, you might be able to use your address in your private LAN network.

If you want to deploy your relay to the cloud, you should set NODE_ADDRESS to your public facing IP, or possibly to your domain name. If you are using a domain name, note that you do not need to obtain a certificate, because Offset uses a different type of authentication.

RELAY_PORT is the public facing port of the relay. You can pick any port number that you want that is at least 1024 1.

Next, we create a directory named relay, that is going to hold all of our relay’s data.

The following command:

stmgr gen-ident --output relay/relay.ident

Generates a new identity for the relay. An identity is a pair of private and public keys. When nodes connect to the relay, the relay will use his private key to prove his identity.

Next, we generate a relay ticket:

stmgr relay-ticket \
        --address $RELAY_ADDRESS:$RELAY_PORT \
        --idfile relay/relay.ident \
        --output relay/relay.relay

A relay ticket is a file containig the relay’s public address and public key. The ticket file allows nodes to connect to the relay. A relay ticket file can also be used inside the Offset mobile app, to configure a new relay.

Finally, the last command:

strelay --idfile relay/relay.ident --laddr$RELAY_PORT &

Starts the relay. The & sign at the end of the command means that the command will run in the background. If this is not what you want, you can omit it.


In most operating systems, ports below 1024 are usually reserved, and require administrator priviledges to use.