Create an offer

If you are the first user to join a room (the person initiating the call), the app creates an offer and tries to store it inside a structured data with an ID based on the name of the room. This offer includes a session description in SDP format, and it needs to be delivered to the call recipient (the person receiving the call).

Contents

Create a new WebRTC peer connection

The app creates a new RTCPeerConnection using the simple-peer module. If you are the first user to join this room, props.peerPayload is false and therefore the value of initiator will be true. This means that the app will create an offer.

PeerView.js

const initiator = !props.peerPayload
const peer = new Peer({ initiator: initiator,
                      stream: props.stream,
                      config : {
                        iceServers: CONFIG.iceServers
                      },
                      trickle: false })

For now, only the connection establishment is done using the SAFE Network. The actual connection is either peer-to-peer (STUN) or via a TURN server. At some point later, we will integrate this functionality directly in CRUST.

Store the offer inside a structured data

After the offer is created, the signal event is fired.

PeerView.js

peer.on('signal', (d) => {
  // try to automatically establish connection
  publishData(targetId, {payload: d, targetId: myNewId})
    .catch(console.log.bind(console))

  if (initiator) {
    let poller = window.setInterval(() => {
      readData(myNewId).then((data) => {
        window.clearInterval(poller)
        peer.signal(data.payload)
      })
    }, 2000) // we poll once every 2 seconds
  }
})

The app tries to create a structured data with an ID based on the name of the room. This structured data will contain the offer as well as a random ID, which will be used to store the answer of the call recipient.

PeerView.js

const targetId = initiator ? props.room : props.peerPayload.targetId
const myNewId = this.props.room + '-' + (Math.random())

Create a structured data

The app creates a structured data handle for the offer.

Create structured data

POST /structured-data

store.js

safeStructuredData.create(ACCESS_TOKEN, address, 500, data)

The address of the structured data is based on the app ID (example.signaling.v1) and the name of the room. The structured data is unversioned (type 500). The data is stored as a base64 string.

store.js

const address = btoa(`${APP_ID}-${name}`)
const data = new Buffer(JSON.stringify(payload)).toString('base64')

Save the structured data

The app saves the structured data by sending a PUT request to the SAFE Network.

Save structured data

PUT /structured-data/:handleId

store.js

safeStructuredData.put(ACCESS_TOKEN, handleId)