snapshot of https://github.com/pion/webrtc.git (main, 2026-09-15; blobs > 131072B omitted)

examples/trickle-ice/README.md

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+# trickle-ice
+trickle-ice demonstrates Pion WebRTC's Trickle ICE APIs.  ICE is the subsystem WebRTC uses to establish connectivity.
+
+Trickle ICE is the process of sharing addresses as soon as they are gathered. This parallelizes
+establishing a connection with a remote peer and starting sessions with TURN servers. Using Trickle ICE
+can dramatically reduce the amount of time it takes to establish a WebRTC connection.
+
+Trickle ICE isn't mandatory to use, but highly recommended.
+
+## Instructions
+
+### Download trickle-ice
+This example requires you to clone the repo since it is serving static HTML.
+
+```
+git clone https://github.com/pion/webrtc.git
+cd webrtc/examples/trickle-ice
+```
+
+### Run trickle-ice
+Execute `go run *.go`
+
+### Open the Web UI
+Open [http://localhost:8080](http://localhost:8080). This will automatically start a PeerConnection.
+
+## Note
+Congrats, you have used Pion WebRTC! Now start building something cool

examples/trickle-ice/index.html

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+<html>
+<!--
+      SPDX-FileCopyrightText: 2026 The Pion community <https://pion.ly>
+      SPDX-License-Identifier: MIT
+  -->
+<head>
+  <title>trickle-ice</title>
+  <style>
+    #iceConnectionStates, #inboundDataChannelMessages {
+      border: 1px solid #ccc;
+      padding: 10px;
+      height: 200px;
+      overflow-y: auto;
+      font-family: monospace;
+      background-color: #f9f9f9;
+    }
+
+    .ice-checking { color: orange; }
+    .ice-connected { color: green; }
+    .ice-disconnected { color: red; }
+    .ice-closed { color: gray; }
+
+
+    .data-msg { margin: 2px 0; }
+  </style>
+</head>
+
+<body>
+<h3>Controls</h3>
+<button id="startBtn">Start</button>
+<button id="stopBtn">Stop</button>
+
+<h3> ICE Connection States </h3>
+<div id="iceConnectionStates"></div> <br />
+
+<h3> Inbound DataChannel Messages </h3>
+<div id="inboundDataChannelMessages"></div>
+</body>
+
+<script>
+  const socket = new WebSocket(`ws://${window.location.host}/websocket`)
+  let pc = null
+  let dc = null
+  let offerCreated = false
+
+  function createPeerConnection() {
+    pc = new RTCPeerConnection({
+      iceServers: [{ urls: 'stun:stun.l.google.com:19302' }]
+    })
+
+
+  // Handle outgoing ICE candidates
+  pc.onicecandidate = e => {
+    if (e.candidate && e.candidate.candidate !== "") {
+      if (socket.readyState === WebSocket.OPEN) {
+        socket.send(JSON.stringify(e.candidate))
+      } else {
+        console.warn("WebSocket not open, candidate not sent")
+      }
+    }
+  }
+  // ICE connection state change handler
+  pc.oniceconnectionstatechange = () => {
+    let el = document.createElement('p')
+    el.appendChild(document.createTextNode(pc.iceConnectionState))
+    el.className = 'ice-' + pc.iceConnectionState.toLowerCase()
+    document.getElementById('iceConnectionStates').appendChild(el);
+  }
+
+    // Incoming DataChannel from remote
+    pc.ondatachannel = event => {
+      dc = event.channel
+      setupDataChannel(dc)
+    }
+  }
+
+    // Setup a DataChannel
+    function setupDataChannel(channel) {
+      channel.onopen = () => console.log("DataChannel open")
+      channel.onmessage = event => {
+        let el = document.createElement('p')
+        el.textContent = `${new Date().toLocaleTimeString()} - ${event.data}`
+        el.className = 'data-msg'
+        document.getElementById('inboundDataChannelMessages').appendChild(el)
+      }
+      channel.onclose = () => console.log("DataChannel closed")
+    }
+
+  // Handle incoming WebSocket messages
+  socket.onmessage = e => {
+    try {
+      let msg = JSON.parse(e.data)
+      if (!msg) return console.log('failed to parse msg')
+      if (msg.candidate) {
+        pc.addIceCandidate(msg)
+      } else {
+        pc.setRemoteDescription(msg)
+      }
+    } catch (err) {
+      console.warn("Failed to parse message:", e.data)
+    }
+  }
+
+  // Start button handler
+  document.getElementById('startBtn').onclick = () => {
+    if (offerCreated) return
+
+    if (!pc) createPeerConnection()
+
+    dc = pc.createDataChannel('data')
+    setupDataChannel(dc)
+
+    pc.createOffer().then(offer => {
+      pc.setLocalDescription(offer)
+      socket.send(JSON.stringify(offer))
+      offerCreated = true
+    })
+  }
+
+  // Stop button handler
+  document.getElementById('stopBtn').onclick = () => {
+    if (dc) {
+      dc.close()
+      console.log("DataChannel closed")
+      dc = null
+      offerCreated = false
+    }
+    if (pc) {
+      // Show disconnected before closing
+      let el = document.createElement('p')
+      el.textContent = `disconnected`
+      el.className = 'ice-disconnected'
+      document.getElementById('iceConnectionStates').appendChild(el)
+
+      setTimeout(() => {
+        pc.close()
+        console.log("PeerConnection closed")
+        el = document.createElement('p')
+        el.textContent = `closed`
+        el.className = 'ice-closed'
+        document.getElementById('iceConnectionStates').appendChild(el)
+        pc = null
+      }, 50) // 50ms delay
+    }
+
+  }
+
+</script>
+</html>

examples/trickle-ice/main.go

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+// SPDX-FileCopyrightText: 2026 The Pion community <https://pion.ly>
+// SPDX-License-Identifier: MIT
+
+// trickle-ice demonstrates Pion WebRTC's Trickle ICE APIs.  ICE is the subsystem WebRTC uses to establish connectivity.
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/pion/webrtc/v4"
+	"golang.org/x/net/websocket"
+)
+
+// websocketServer is called for every new inbound WebSocket
+// nolint: gocognit, cyclop
+func websocketServer(wsConn *websocket.Conn) {
+	// Create a new RTCPeerConnection
+	peerConnection, err := webrtc.NewPeerConnection(webrtc.Configuration{})
+	if err != nil {
+		panic(err)
+	}
+
+	// When Pion gathers a new ICE Candidate send it to the client. This is how
+	// ice trickle is implemented. Everytime we have a new candidate available we send
+	// it as soon as it is ready. We don't wait to emit a Offer/Answer until they are
+	// all available
+	peerConnection.OnICECandidate(func(candidate *webrtc.ICECandidate) {
+		if candidate == nil {
+			return
+		}
+
+		outbound, marshalErr := json.Marshal(candidate.ToJSON())
+		if marshalErr != nil {
+			fmt.Println("Marshal ICECandidate error:", marshalErr)
+
+			return
+		}
+
+		if _, err = wsConn.Write(outbound); err != nil {
+			fmt.Println("WebSocket write error:", err)
+
+			return
+		}
+	})
+
+	// 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() {
+			fmt.Println(time.Now().Format("15:04:05"), "- DataChannel open")
+			// Periodically send timestamped messages
+			go func() {
+				ticker := time.NewTicker(time.Second * 3)
+				defer ticker.Stop()
+				for range ticker.C {
+					if err := d.SendText(time.Now().String()); err != nil {
+						fmt.Println(time.Now().Format("15:04:05"), "- DataChannel closed, stopping send loop")
+
+						return
+					}
+				}
+			}()
+		})
+	})
+
+	buf := make([]byte, 1500)
+	for {
+		// Read each inbound WebSocket Message
+		n, err := wsConn.Read(buf)
+		if err != nil {
+			fmt.Println(time.Now().Format("15:04:05"), "- WebSocket read error:", err)
+
+			return
+		}
+
+		// Unmarshal each inbound WebSocket message
+		var (
+			candidate webrtc.ICECandidateInit
+			offer     webrtc.SessionDescription
+		)
+
+		switch {
+		// Attempt to unmarshal as a SessionDescription. If the SDP field is empty
+		// assume it is not one.
+		case json.Unmarshal(buf[:n], &offer) == nil && offer.SDP != "":
+			if err = peerConnection.SetRemoteDescription(offer); err != nil {
+				fmt.Println("SetRemoteDescription error:", err)
+
+				return
+			}
+
+			answer, answerErr := peerConnection.CreateAnswer(nil)
+			if answerErr != nil {
+				fmt.Println("CreateAnswer error:", err)
+
+				return
+			}
+
+			if err = peerConnection.SetLocalDescription(answer); err != nil {
+				fmt.Println("SetLocalDescription error:", err)
+
+				return
+			}
+
+			outbound, marshalErr := json.Marshal(answer)
+			if marshalErr != nil {
+				fmt.Println("Marshal answer error:", err)
+
+				return
+			}
+
+			if _, err = wsConn.Write(outbound); err != nil {
+				fmt.Println("WebSocket write error:", err)
+
+				return
+			}
+		// Attempt to unmarshal as a ICECandidateInit. If the candidate field is empty
+		// assume it is not one.
+		case json.Unmarshal(buf[:n], &candidate) == nil && candidate.Candidate != "":
+			if err = peerConnection.AddICECandidate(candidate); err != nil {
+				fmt.Println("AddICECandidate error:", err)
+
+				return
+			}
+		default:
+			fmt.Println("Unknown WebSocket message")
+		}
+	}
+}
+
+func main() {
+	http.Handle("/", http.FileServer(http.Dir(".")))
+	http.Handle("/websocket", websocket.Handler(websocketServer))
+
+	fmt.Println("Open http://localhost:8080 to access this demo")
+	// nolint: gosec
+	panic(http.ListenAndServe(":8080", nil))
+}