github.com/bringyour/webrtc-conn

WebRTC Conn

WebRTC Conn is a Go library that seamlessly integrates the Pion WebRTC library with the net.Conn interface. This allows developers to easily incorporate WebRTC data channels into applications that rely on traditional network connections.

WebRTC is a powerful yet complex protocol, involving intricate message flows to establish peer-to-peer connections. WebRTC Conn abstracts away these complexities, providing a straightforward adapter that presents WebRTC data channels as standard net.Conn interfaces.

Features

• Seamless WebRTC Integration: Leverage the power of WebRTC for reliable peer-to-peer communication.
• net.Conn Compatibility: Treat WebRTC data channels as standard net.Conn connections, simplifying integration with existing codebases.
• Flexible Channel Configuration: Customize data channel properties such as message ordering and retransmission limits to meet your application's requirements.

Usage

Roles in WebRTC Connection

A WebRTC connection involves two primary roles:

1. Offer: The initiator of the connection, responsible for opening the data channel and configuring its parameters.
2. Answer: The responder, which joins the data channel established by the Offer.

Exchanging SDP and ICE Candidates

To establish a WebRTC connection, Offer/Answer Session Description Protocol (SDP) messages must be exchanged between peers, along with ICE (Interactive Connectivity Establishment) candidates. WebRTC does not define a specific transport mechanism for this exchange, so you can implement it using protocols like WebSockets.

WebRTC Conn provides a transport-agnostic approach through the following interfaces, allowing you to define your own transport mechanism:

type OfferSync interface {
    // OfferSDP sends the offer SDP and receives the answer SDP.
    OfferSDP(ctx context.Context, offer webrtc.SessionDescription) (webrtc.SessionDescription, error)

    // GetAnswerPeerCandidates retrieves ICE candidates from the answering peer.
    GetAnswerPeerCandidates(ctx context.Context) ([]webrtc.ICECandidate, error)

    // AddOfferPeerCandidate adds an ICE candidate for the answering peer.
    AddOfferPeerCandidate(ctx context.Context, candidate webrtc.ICECandidate) error
}

type AnswerSync interface {
    // AnswerSDP handles the offer SDP and generates the answer SDP.
    AnswerSDP(ctx context.Context, answer func(ctx context.Context, offer webrtc.SessionDescription) (webrtc.SessionDescription, error)) error

    // GetOfferPeerCandidates retrieves ICE candidates from the offering peer.
    GetOfferPeerCandidates(ctx context.Context) ([]webrtc.ICECandidate, error)

    // AddAnswerPeerCandidate adds an ICE candidate for the offering peer.
    AddAnswerPeerCandidate(ctx context.Context, candidate webrtc.ICECandidate) error
}

Creating an Offer

To create an offer, use the webrtcconn.Offer function. It requires a context, a webrtc.Configuration object for the peer connection, an implementation of the OfferSync interface, a flag to indicate whether RTCP (Real-time Transport Control Protocol) should be used to detect and retransmit lost packets, the maximum number of retransmissions, and a connection timeout.

oc, err := webrtcconn.Offer(
    ctx, 
    webrtc.Configuration{}, 
    offerSync,
    true,
    2,
    15*time.Second,
)
if err != nil {
    return err
}

Responding to an Offer

To respond to an offer, use the webrtcconn.Answer function. Similar to the offer process, it requires a context, a webrtc.Configuration object, an implementation of the AnswerSync interface, and a connection timeout.

ac, err := webrtcconn.Answer(
    ctx, 
    webrtc.Configuration{}, 
    answerSync,
    15*time.Second,
)
if err != nil {
    return err
}

Data Channel Configuration

When establishing a connection, the Offer role defines the data channel's configuration, including:

• Ordered: Specifies whether messages should be delivered in the order they were sent.
• Max Retransmits: Sets the maximum number of retransmission attempts for unreliable data channels.