Add experimental support for ICE TCP

See pion/ice issue and PR:

- https://github.com/pion/ice/tree/issue-196
- https://github.com/pion/ice/pull/226

examples/ice-tcp/main.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/pion/webrtc/v3"
+)
+
+var peerConnection *webrtc.PeerConnection //nolint
+
+func doSignaling(w http.ResponseWriter, r *http.Request) {
+	var err error
+
+	if peerConnection == nil {
+		m := webrtc.MediaEngine{}
+		m.RegisterDefaultCodecs()
+
+		settingEngine := webrtc.SettingEngine{}
+
+		// Enable support only for TCP ICE candidates.
+		settingEngine.SetNetworkTypes([]webrtc.NetworkType{
+			webrtc.NetworkTypeTCP4,
+			webrtc.NetworkTypeTCP6,
+		})
+		settingEngine.SetICETCPPort(8443)
+
+		api := webrtc.NewAPI(
+			webrtc.WithMediaEngine(m),
+			webrtc.WithSettingEngine(settingEngine),
+		)
+		if peerConnection, err = api.NewPeerConnection(webrtc.Configuration{}); 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())
+		})
+
+		// Send the current time via a DataChannel to the remote peer every 3 seconds
+		peerConnection.OnDataChannel(func(d *webrtc.DataChannel) {
+			d.OnOpen(func() {
+				for range time.Tick(time.Second * 3) {
+					if err = d.SendText(time.Now().String()); err != nil {
+						panic(err)
+					}
+				}
+			})
+		})
+	}
+
+	var offer webrtc.SessionDescription
+	if err = json.NewDecoder(r.Body).Decode(&offer); err != nil {
+		panic(err)
+	}
+
+	if err = peerConnection.SetRemoteDescription(offer); err != nil {
+		panic(err)
+	}
+
+	// Create channel that is blocked until ICE Gathering is complete
+	gatherComplete := webrtc.GatheringCompletePromise(peerConnection)
+
+	answer, err := peerConnection.CreateAnswer(nil)
+	if err != nil {
+		panic(err)
+	} else if err = peerConnection.SetLocalDescription(answer); 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
+
+	response, err := json.Marshal(*peerConnection.LocalDescription())
+	if err != nil {
+		panic(err)
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	if _, err := w.Write(response); err != nil {
+		panic(err)
+	}
+}
+
+func main() {
+	http.Handle("/", http.FileServer(http.Dir(".")))
+	http.HandleFunc("/doSignaling", doSignaling)
+
+	fmt.Println("Open http://localhost:8080 to access this demo")
+	panic(http.ListenAndServe(":8080", nil))
+}