pion-to-pion example, passing description without http server

answer.go

package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"net/http"
	"time"
    "strings"

    "os"
    "bytes"
    "bufio"

	"github.com/pion/webrtc/v2"

	"github.com/pion/webrtc/v2/examples/internal/signal"
)

func main() {
	flag.Parse()

	// 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)
	}

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

	// 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 := signal.RandSeq(15)
				fmt.Printf("Sending '%s'\n", message)

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

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

    var offerText string
    scanner := bufio.NewScanner(os.Stdin)
    for scanner.Scan() {
        offerText = scanner.Text()
        fmt.Println("read", offerText)
        break
    }

    if scanner.Err() != nil {
        panic(scanner.Err())
    }


    var offer webrtc.SessionDescription
    err = json.NewDecoder(strings.NewReader(offerText)).Decode(&offer)
	// Exchange the offer/answer via HTTP
	// offerChan, answerChan := mustSignalViaHTTP(*addr)

	// Wait for the remote SessionDescription
	// offer = <-offerChan
    fmt.Println(offer)

	err = peerConnection.SetRemoteDescription(offer)
	if err != nil {
		panic(err)
	}

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

    answerBuf := new(bytes.Buffer)
    err = json.NewEncoder(answerBuf).Encode(answer)
    if err != nil {
        panic(err)
    }

    println(answerBuf.String())


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

	// Send the answer
	// answerChan <- answer

	// Block forever
	select {}
}

// mustSignalViaHTTP exchange the SDP offer and answer using an HTTP server.
func mustSignalViaHTTP(address string) (offerOut chan webrtc.SessionDescription, answerIn chan webrtc.SessionDescription) {
	offerOut = make(chan webrtc.SessionDescription)
	answerIn = make(chan webrtc.SessionDescription)

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		var offer webrtc.SessionDescription
		err := json.NewDecoder(r.Body).Decode(&offer)
		if err != nil {
			panic(err)
		}

		offerOut <- offer
		answer := <-answerIn

		err = json.NewEncoder(w).Encode(answer)
		if err != nil {
			panic(err)
		}

	})

	go func() {
		panic(http.ListenAndServe(address, nil))
	}()
	fmt.Println("Listening on", address)

	return
}

offer.go

package main

import (
	"bytes"
	"encoding/json"
	"flag"
	"fmt"
	"net/http"
    "os"
    "bufio"
    "strings"
	"time"

	"github.com/pion/webrtc/v2"

	"github.com/pion/webrtc/v2/examples/internal/signal"
)

func main() {
	flag.Parse()

	// 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)
	}

	// Create a datachannel with label 'data'
	dataChannel, err := peerConnection.CreateDataChannel("data", nil)
	if err != nil {
		panic(err)
	}

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

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

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

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

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

	// Create an offer to send to the browser
	offer, err := peerConnection.CreateOffer(nil)
	if err != nil {
		panic(err)
	}

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

    b := new (bytes.Buffer)
    err = json.NewEncoder(b).Encode(offer)
    if err != nil {
        panic(err)
    }

    fmt.Println(b)

	// Exchange the offer for the answer
	// answer := mustSignalViaHTTP(offer, *addr)
    var answerText string
    scanner := bufio.NewScanner(os.Stdin)
    for scanner.Scan() {
        answerText = scanner.Text()
        fmt.Println("read", answerText)
    }

    if scanner.Err() != nil {
        panic(scanner.Err())
    }

    var answer webrtc.SessionDescription
    err = json.NewDecoder(strings.NewReader(answerText)).Decode(&answer)
    if err != nil {
        panic(err)
    }

	// Apply the answer as the remote description
	err = peerConnection.SetRemoteDescription(answer)
	if err != nil {
		panic(err)
	}

	// Block forever
	select {}
}

// mustSignalViaHTTP exchange the SDP offer and answer using an HTTP Post request.
func mustSignalViaHTTP(offer webrtc.SessionDescription, address string) webrtc.SessionDescription {
	b := new(bytes.Buffer)
	err := json.NewEncoder(b).Encode(offer)
	if err != nil {
		panic(err)
	}

	resp, err := http.Post("http://"+address, "application/json; charset=utf-8", b)
	if err != nil {
		panic(err)
	}
	defer func() {
		closeErr := resp.Body.Close()
		if closeErr != nil {
			panic(closeErr)
		}
	}()

	var answer webrtc.SessionDescription
	err = json.NewDecoder(resp.Body).Decode(&answer)
	if err != nil {
		panic(err)
	}

	return answer
}