This is a prototype of doing live broadcasting using WebRTC.

The server is written in Go. To build it check it out under your Go path:

mkdir -p $GOPATH/src/github.com/comoyo
cd $GOPATH/src/github.com/comoyo
git clone git@github.com:comoyo/tributary.git

Install and run the server:

go get github.com/comoyo/tributary/tributary-server/...
go install github.com/comoyo/tributary/tributary-server
tributary-server

We use webpack for development (and webpack-dev-server).

To install, run

npm install -g webpack webpack-dev-server
npm install

Then run webpack-dev-server --inline from the web directory to serve files and watch for changes.

Go to http://localhost:8080 to see the magic.

The web client and server talk over web sockets. All of the messages sent back and forth are JSON objects with a property "command" which defines the type of the message. Clients are either "broadcasting clients" (i.e. the person broadcasting the event) or "receiving clients" (i.e. the people consuming a live broadcast).

The client requests configuration parameters from the server.

The server will send back a FETCH_CONFIG_RECEIVED command with the following properties:

• iceServers (array): an array of ICE servers that can be passed in as part of an RTCPeerConnection constructor.

A broadcasting client sends this command to announce the intent to start a live broadcast.

Command properties:

• name (string): an identifier for the broadcast.
• peerName (string): a user-friendly name for the client doing the broadcasting.

The server will send back a START_BROADCAST_RECEIVED command which is an acknowledgement that the broadast is now live.

A broadcasting client sends this command to terminate the live broadcast.

Command properties:

• name (string): an identifier for the broadcast.

The server will send back a END_BROADCAST_RECEIVED command which is an acknowledgement that the broadast is now terminated.

A receiving client sends this message to announce that they'd like to watch a live broadcast.

Command properties:

• name (string): an identifier for the broadcast.
• offer (JSON object): the offer retrieved via RTCPeerConnection.createOffer().
• peerName (string): a user-friendly name for the client listening to the broadcast.

The server will send back a JOIN_BROADCAST_RECEIVED to this command. It will contain the following properties:

• peer (string): a unique identifier of the remote peer. The client will need to send this ID back to the server for future messages (like ICE_CANDIDATE).
• answer (JSON object): the answer from a remote peer which will start sending the broadcast.

A receiving client sends this message to cleanly exit a broadcast.

Command properties:

• name (string): an identifier for the broadcast.

The server will send back a LEAVE_BROADCAST_RECEIVED command which is an acknowledgement that the broadast has been exited.

A client (both broadcasting and receiving) sends this message to announce that is has one or more ICE candidates.

Command properties:

• peer (string): the unique identifier of the remote peer that was provided in the JOIN_BROADCAST_RECEIVED message.
• candidates (array of JSON objects): the ICE candidates from the RTCPeerConnection.onicecandidate().

The server will send back a ICE_CANDIDATES_RECEIVED to acknowlege that the remote peer has received the candidates.

A client can send this to listen to changes about the state of the tree

Command properties:

• name (string): an identifier for the broadcast.

The server will send the client TREE_STATE_CHANGED messages whenever the tree changes.

A client can send this to stop listening to changes about the state of the tree

Command properties:

• name (string): an identifier for the broadcast.

A new listener is attempting to start receiving the broadcast from this client (which could be the oringal broadcasting client or some other client further down the tree).

Command properties:

• peer (string): a unique identifier of the remote peer. The client will need to send this ID back to the server for future messages (like ICE_CANDIDATE).
• offer (JSON object): the offer from the remote peer.

The server expects an RELAY_BROADCAST_RECEIVED message in response. It will contain the following properties:

• peer (string): a unique identifier of the remote peer.
• answer (JSON object): the answer to send the remote peer obtained via RTCPeerConnection.createAnswer().

The remote peer is sending one or more ICE candidates.

Command properties:

• peer (string): the unique identifer of the remote peer providing ICE candidates.
• candidates (array of JSON objects): the ICE candidates from the remote peer which should be passed to RTCPeerConnection.addIceCandidate().

The server expects an ICE_CANDIDATES_RECEIVED message to acknowledge the receipt of the ICE candidate.

A notification from the server that the broadcaster has ended the broadcast

Command properties:

• name (string): an identifier for the broadcast.

The server sends this message to notify a client that it's upstream peer is dead and that it needs to reconnect in order to keep viewing the broadcast. It is then the client's job to pass along the stream from the new peer to it's downstream listeners.

Notifies a client that changes to the tree have occurred.

Command properties:

• tree (JSON object): the full tree of the broadcast.