Webrtc Data Channel always in connecting state and not open

Hi,

I am trying to send message using webrtc datachannel in go lang. But the ready state of data channel is always connecting . So, I am unable to send message. Can anyone help me to find the issue?

package main

import (
	"fmt"
	"log"

	"<http://github.com/pion/webrtc/v3|github.com/pion/webrtc/v3>"
)

func main() {
	// Set up a WebRTC connection
	peerConnection, err := webrtc.NewPeerConnection(webrtc.Configuration{
		ICEServers: []webrtc.ICEServer{
			{
				URLs: []string{"stun:<http://stun.l.google.com:19302%22|stun.l.google.com:19302">},
			},
		},
	})
	if err != nil {
		log.Fatal(err)
	}

	// Set up a data channel
	dataChannel, err := peerConnection.CreateDataChannel("myDataChannel", nil)
	if err != nil {
		log.Fatal(err)
	}

	// Set up channel message handlers
	dataChannel.OnOpen(func() {
		fmt.Println("Data channel opened")
	})
	dataChannel.OnMessage(func(msg webrtc.DataChannelMessage) {
		fmt.Printf("Message from data channel: %s\n", string(msg.Data))
	})

	fmt.Println(dataChannel.ReadyState())
	
	// Send a message over the data channel
	message := []byte("Hello, world!")
	if err := dataChannel.Send(message); err != nil {
		log.Fatal(err)
	}

	// Close the connection when the program is finished
	defer peerConnection.Close()

	// Wait indefinitely
	select {}
}

This doesn’t look like a valid URL. Does it actually look like this in your code, or did somethingbhappen in the copy-paste into this forum?

This example works for me, only to see this example: webrtc/examples/data-channels at master · pion/webrtc · GitHub

package main

import (
	"bufio"
	"bytes"
	"compress/gzip"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"strings"
	"time"

	"github.com/pion/randutil"
	"github.com/pion/webrtc/v3"
)

const compress = false

func main() {
	// Everything below is the Pion WebRTC API! Thanks for using it ❤️.

	// Prepare the configuration
	config := webrtc.Configuration{
		ICEServers: []webrtc.ICEServer{
			{
				URLs: []string{"stun:stun.l.google.com:19302"},
			},
		},
	}

	// Create a new RTCPeerConnection
	peerConnection, err := webrtc.NewPeerConnection(config)
	if err != nil {
		panic(err)
	}
	defer func() {
		if cErr := peerConnection.Close(); cErr != nil {
			fmt.Printf("cannot close peerConnection: %v\n", cErr)
		}
	}()

	// Set the handler for Peer connection state
	// This will notify you when the peer has connected/disconnected
	peerConnection.OnConnectionStateChange(func(s webrtc.PeerConnectionState) {
		fmt.Printf("Peer Connection State has changed: %s\n", s.String())

		if s == webrtc.PeerConnectionStateFailed {
			// Wait until PeerConnection has had no network activity for 30 seconds or another failure. It may be reconnected using an ICE Restart.
			// Use webrtc.PeerConnectionStateDisconnected if you are interested in detecting faster timeout.
			// Note that the PeerConnection may come back from PeerConnectionStateDisconnected.
			fmt.Println("Peer Connection has gone to failed exiting")
			os.Exit(0)
		}
	})

	// Register data channel creation handling
	peerConnection.OnDataChannel(func(d *webrtc.DataChannel) {
		fmt.Printf("New DataChannel %s %d\n", d.Label(), d.ID())

		// Register channel opening handling
		d.OnOpen(func() {
			fmt.Printf("Data channel '%s'-'%d' open. Random messages will now be sent to any connected DataChannels every 5 seconds\n", d.Label(), d.ID())

			for range time.NewTicker(5 * time.Second).C {
				message := RandSeq(15)
				fmt.Printf("Sending '%s'\n", message)

				// Send the message as text
				sendErr := d.SendText(message)
				if sendErr != nil {
					panic(sendErr)
				}
			}
		})

		// Register text message handling
		d.OnMessage(func(msg webrtc.DataChannelMessage) {
			fmt.Printf("Message from DataChannel '%s': '%s'\n", d.Label(), string(msg.Data))
		})
	})

	// Wait for the offer to be pasted
	offer := webrtc.SessionDescription{}
	Decode(MustReadStdin(), &offer)

	// Set the remote SessionDescription
	err = peerConnection.SetRemoteDescription(offer)
	if err != nil {
		panic(err)
	}

	// Create an answer
	answer, err := peerConnection.CreateAnswer(nil)
	if err != nil {
		panic(err)
	}

	// Create channel that is blocked until ICE Gathering is complete
	gatherComplete := webrtc.GatheringCompletePromise(peerConnection)

	// Sets the LocalDescription, and starts our UDP listeners
	err = peerConnection.SetLocalDescription(answer)
	if err != nil {
		panic(err)
	}

	// Block until ICE Gathering is complete, disabling trickle ICE
	// we do this because we only can exchange one signaling message
	// in a production application you should exchange ICE Candidates via OnICECandidate
	<-gatherComplete

	// Output the answer in base64 so we can paste it in browser
	fmt.Println(Encode(*peerConnection.LocalDescription()))

	// Block forever
	select {}
}

func RandSeq(n int) string {
	val, err := randutil.GenerateCryptoRandomString(n, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
	if err != nil {
		panic(err)
	}

	return val
}

func Decode(in string, obj interface{}) {
	b, err := base64.StdEncoding.DecodeString(in)
	if err != nil {
		panic(err)
	}

	if compress {
		b = unzip(b)
	}

	err = json.Unmarshal(b, obj)
	if err != nil {
		panic(err)
	}
}

func MustReadStdin() string {
	r := bufio.NewReader(os.Stdin)

	var in string
	for {
		var err error
		in, err = r.ReadString('\n')
		if err != io.EOF {
			if err != nil {
				panic(err)
			}
		}
		in = strings.TrimSpace(in)
		if len(in) > 0 {
			break
		}
	}

	fmt.Println("")

	return in
}

func Encode(obj interface{}) string {
	b, err := json.Marshal(obj)
	if err != nil {
		panic(err)
	}

	if compress {
		b = zip(b)
	}

	return base64.StdEncoding.EncodeToString(b)
}

func zip(in []byte) []byte {
	var b bytes.Buffer
	gz := gzip.NewWriter(&b)
	_, err := gz.Write(in)
	if err != nil {
		panic(err)
	}
	err = gz.Flush()
	if err != nil {
		panic(err)
	}
	err = gz.Close()
	if err != nil {
		panic(err)
	}
	return b.Bytes()
}

func unzip(in []byte) []byte {
	var b bytes.Buffer
	_, err := b.Write(in)
	if err != nil {
		panic(err)
	}
	r, err := gzip.NewReader(&b)
	if err != nil {
		panic(err)
	}
	res, err := ioutil.ReadAll(r)
	if err != nil {
		panic(err)
	}
	return res
}