Pion data channel example

main.go

package main

import (
	"encoding/json"
	"log"
	"time"

	"github.com/pion/webrtc/v2"
)

func check(err error) {
	if err != nil {
		panic(err)
	}
}

// EndpointListener ...
type EndpointListener struct {
	OnDescription chan string
	OnBye         chan bool
}

// Endpoint ...
type Endpoint struct {
	PC          *webrtc.PeerConnection
	Listener    *EndpointListener
	IsInitiator bool

	dataChs map[string]*webrtc.DataChannel
}

// NewEndpoint ...
func NewEndpoint() *Endpoint {
	// Prepare the configuration
	config := webrtc.Configuration{
		ICEServers: []webrtc.ICEServer{},
	}

	// Create a new PeerConnection
	pc, err := webrtc.NewPeerConnection(config)
	check(err)

	return &Endpoint{
		PC: pc,
		Listener: &EndpointListener{
			OnDescription: make(chan string),
			OnBye:         make(chan bool),
		},
		IsInitiator: false,
		dataChs:     map[string]*webrtc.DataChannel{},
	}
}

// Start assigns this epoint as an initiator and triggers sendding an offer.
func (ep *Endpoint) Start() {
	var msgID = 0
	buf := make([]byte, 1000)
	ep.IsInitiator = true

	ordered := false
	maxRetransmits := uint16(0)

	options := &webrtc.DataChannelInit{
		Ordered:        &ordered,
		MaxRetransmits: &maxRetransmits,
	}

	// Create a datachannel with label 'data'
	dc, err := ep.PC.CreateDataChannel("data", options)
	check(err)

	// Register channel opening handling
	dc.OnOpen(func() {
		log.Printf("OnOpen: %s-%d. Random messages will now be sent to any connected DataChannels every second\n", dc.Label(), dc.ID())

		for range time.NewTicker(1000 * time.Millisecond).C {
			log.Printf("Sending (%d) msg with len %d \n", msgID, len(buf))
			msgID++

			err := dc.Send(buf)
			check(err)
		}
	})

	// Register the OnMessage to handle incoming messages
	dc.OnMessage(func(dcMsg webrtc.DataChannelMessage) {
		if dcMsg.IsString {
			log.Printf("Message (string) from DataChannel '%s' payload '%s'\n", dc.Label(), string(dcMsg.Data))
		} else {
			log.Printf("Message ([]byte) from DataChannel '%s' with length %d\n", dc.Label(), len(dcMsg.Data))
		}
	})

	ep.dataChs[dc.Label()] = dc

	// Now, create an offer
	offer, err := ep.PC.CreateOffer(nil)
	check(err)

	ep.PC.SetLocalDescription(offer)

	desc, err := json.Marshal(offer)
	check(err)

	go func() {
		ep.Listener.OnDescription <- string(desc)
	}()
}

// OnRemoteDescription ...
func (ep *Endpoint) OnRemoteDescription(sdp string) {
	var desc webrtc.SessionDescription
	bytes := []byte(sdp)
	err := json.Unmarshal(bytes, &desc)
	check(err)

	// Apply the desc as the remote description
	err = ep.PC.SetRemoteDescription(desc)
	check(err)

	if ep.IsInitiator {
		return
	}

	// Set callback for new data channels
	ep.PC.OnDataChannel(func(dc *webrtc.DataChannel) {
		// Register channel opening handling
		dc.OnOpen(func() {
			log.Printf("OnOpen: %s-%d. Random messages will now be sent to any connected DataChannels every second\n", dc.Label(), dc.ID())
		})

		// Register the OnMessage to handle incoming messages
		dc.OnMessage(func(dcMsg webrtc.DataChannelMessage) {
			if dcMsg.IsString {
				log.Printf("Message (string) from DataChannel '%s' payload '%s'\n", dc.Label(), string(dcMsg.Data))
			} else {
				log.Printf("Message ([]byte) from DataChannel '%s' with length %d\n", dc.Label(), len(dcMsg.Data))
			}
		})

		ep.dataChs[dc.Label()] = dc
	})

	answer, err := ep.PC.CreateAnswer(nil)
	check(err)

	ep.PC.SetLocalDescription(answer)

	desc2, err := json.Marshal(answer)
	check(err)

	go func() {
		ep.Listener.OnDescription <- string(desc2)
	}()
}

func main() {
	ep1 := NewEndpoint()
	ep2 := NewEndpoint()

	ep1.Start()

	for {
		// Block forever
		select {
		case sig := <-ep1.Listener.OnDescription:
			log.Printf("EP1 => EP2:\n%s\n", sig)
			ep2.OnRemoteDescription(sig)
		case <-ep1.Listener.OnBye:
		case sig := <-ep2.Listener.OnDescription:
			log.Printf("EP2 => EP1:\n%s\n", sig)
			ep1.OnRemoteDescription(sig)
		case <-ep1.Listener.OnBye:
		}
	}
}

go.mod for the example code above to build:

pion/webrtc/v2@v2.0.27

module github.com/enobufs/pion-examples/simple-dc

go 1.12

require (
	github.com/golang/mock v1.3.1 // indirect
	github.com/golang/protobuf v1.3.2 // indirect
	github.com/kr/pretty v0.1.0 // indirect
	github.com/lucas-clemente/quic-go v0.11.2 // indirect
	github.com/marten-seemann/qtls v0.3.2 // indirect
	github.com/onsi/ginkgo v1.8.0 // indirect
	github.com/onsi/gomega v1.5.0 // indirect
	github.com/pion/webrtc/v2 v2.0.27
	golang.org/x/crypto v0.0.0-20190701094942-4def268fd1a4 // indirect
	golang.org/x/net v0.0.0-20190724013045-ca1201d0de80 // indirect
	golang.org/x/sys v0.0.0-20190730183949-1393eb018365 // indirect
	golang.org/x/text v0.3.2 // indirect
	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect
	gopkg.in/yaml.v2 v2.2.2 // indirect
)

Run

go run main.go