learn-webrtc/receiver.html at main · arifulislamat/learn-webrtc · GitHub

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<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>WebRTC Receiver — Manual Signaling</title>
    <style>
      *,
      *::before,
      *::after {
        box-sizing: border-box;
      }
      body {
        font-family:
          -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica,
          Arial, sans-serif;
        max-width: 720px;
        margin: 0 auto;
        padding: 24px 20px;
        color: #1a1a2e;
        background: #fafbfc;
        line-height: 1.5;
      }
      h1 {
        margin: 0 0 4px;
        font-size: 1.6rem;
      }
      .subtitle {
        color: #666;
        font-size: 0.9rem;
        margin: 0 0 16px;
      }
      textarea {
        width: 100%;
        height: 60px;
        margin: 6px 0;
        padding: 10px;
        font-family: "SF Mono", "Fira Code", "Cascadia Code", monospace;
        font-size: 12px;
        border: 1px solid #d0d7de;
        border-radius: 6px;
        resize: vertical;
        transition: border-color 0.15s;
      }
      textarea:focus {
        outline: none;
        border-color: #0969da;
        box-shadow: 0 0 0 3px rgba(9, 105, 218, 0.15);
      }
      button {
        padding: 8px 18px;
        margin: 6px 4px 6px 0;
        cursor: pointer;
        border: 1px solid #d0d7de;
        border-radius: 6px;
        background: #f6f8fa;
        font-size: 0.85rem;
        font-weight: 500;
        transition: all 0.15s;
      }
      button:hover:not(:disabled) {
        background: #404142;
        color: #fff;
        border-color: #161616;
      }
      button:disabled {
        opacity: 0.5;
        cursor: not-allowed;
      }
      .step {
        border: 1px solid #d0d7de;
        padding: 16px 20px;
        margin: 12px 0;
        border-radius: 10px;
        background: #fff;
      }
      .step h3 {
        margin: 0 0 8px;
        font-size: 1rem;
        color: #24292f;
      }
      .step p {
        margin: 0 0 10px;
        font-size: 0.88rem;
        color: #57606a;
      }
      #status {
        padding: 10px 14px;
        background: #ddf4ff;
        border: 1px solid #54aeff44;
        border-radius: 6px;
        margin: 12px 0;
        font-size: 0.88rem;
        font-weight: 500;
      }
      #chatSection {
        display: none;
      }
      #receivedMessages {
        border: 1px solid #d0d7de;
        border-radius: 6px;
        padding: 12px;
        min-height: 100px;
        max-height: 300px;
        overflow-y: auto;
        background: #fff;
        margin-bottom: 10px;
      }
      #receivedMessages p {
        margin: 3px 0;
        font-size: 0.9rem;
      }
      #receivedMessages .sent {
        color: #0550ae;
      }
      #receivedMessages .received {
        color: #1a7f37;
      }
      footer {
        margin-top: 32px;
        padding-top: 16px;
        border-top: 1px solid #d8dee4;
        text-align: center;
        font-size: 0.82rem;
        color: #656d76;
      }
      footer a {
        color: #0969da;
        text-decoration: none;
      }
      footer a:hover {
        text-decoration: underline;
      }
      nav {
        margin-bottom: 20px;
        font-size: 0.85rem;
      }
      nav a {
        color: #0969da;
        text-decoration: none;
        margin-right: 12px;
      }
      nav a:hover {
        text-decoration: underline;
      }
      nav a.active {
        font-weight: 600;
        text-decoration: underline;
      }
      .troubleshoot {
        display: none;
        border: 1px solid #cf222e44;
        background: #ffebe9;
        padding: 14px 18px;
        border-radius: 8px;
        margin: 12px 0;
        font-size: 0.85rem;
        color: #24292f;
        line-height: 1.6;
      }
      .troubleshoot summary {
        cursor: pointer;
        font-weight: 600;
        color: #cf222e;
        margin-bottom: 6px;
      }
      .troubleshoot code {
        background: #cf222e11;
        padding: 2px 6px;
        border-radius: 4px;
        font-size: 0.85em;
      }
      .troubleshoot ol {
        padding-left: 18px;
        margin: 8px 0;
      }
      .troubleshoot li {
        margin: 4px 0;
      }
    </style>
  </head>
  <body>
    <h1>Receiver Device</h1>
    <p class="subtitle">
      Manual signaling mode — paste the sender's offer to establish connection
    </p>
    <div id="status">Status: Waiting for offer...</div>

    <!-- Troubleshooting banner (shown on ICE failure) -->
    <div id="troubleshoot" class="troubleshoot">
      <details open>
        <summary>Connection failed — ICE disconnected</summary>
        <p>
          <strong>Brave / Chromium-based browsers</strong> anonymize local IPs
          with <code>.local</code> mDNS addresses for privacy. In manual
          copy-paste mode, the other tab can't resolve these addresses, so
          connectivity checks fail.
        </p>
        <p><strong>Fixes (pick one):</strong></p>
        <ol>
          <li>
            <strong>Use the auto-signaling mode instead</strong> — run
            <code>node server.js</code> and open
            <a href="http://localhost:8080">localhost:8080</a> in two tabs.
            Trickle ICE + localhost works reliably in Brave.
          </li>
          <li>
            <strong>Disable mDNS anonymization in Brave:</strong> go to
            <code>brave://flags/#enable-webrtc-hide-local-ips-with-mdns</code> →
            set to <strong>Disabled</strong> → relaunch Brave.
          </li>
          <li>
            <strong>Lower Brave Shields</strong> for this page (click the lion
            icon → toggle Shields off).
          </li>
        </ol>
      </details>
    </div>

    <!-- STEP 1: Paste offer from sender -->
    <div class="step">
      <h3>Step 1: Paste Offer from Sender</h3>
      <p>
        Paste the offer you copied from the <b>Sender</b> page, then click "Set
        Offer & Create Answer".
      </p>
      <textarea
        id="offerInput"
        placeholder="Paste the offer from the sender here..."
      ></textarea>
      <button id="setOfferBtn">Set Offer & Create Answer</button>
    </div>

    <!-- STEP 2: Copy answer back to sender -->
    <div class="step">
      <h3>Step 2: Copy Answer back to Sender</h3>
      <p>
        Once the answer appears below, copy it and paste it in the Sender page.
      </p>
      <textarea
        id="answerOutput"
        readonly
        placeholder="Answer SDP will appear here..."
      ></textarea>
      <button id="copyAnswerBtn" disabled>Copy Answer to Clipboard</button>
    </div>

    <!-- STEP 3: Chat -->
    <div id="chatSection" class="step">
      <h3>Chat (Data Channel)</h3>
      <div id="receivedMessages"></div>
      <textarea
        id="messageInput"
        placeholder="Type your message..."
        style="height: 40px"
      ></textarea>
      <button id="sendMessageButton">Send Message</button>
    </div>

    <script>
      // ========== DOM Elements ==========
      const statusDiv = document.getElementById("status");
      const offerInput = document.getElementById("offerInput");
      const answerOutput = document.getElementById("answerOutput");
      const setOfferBtn = document.getElementById("setOfferBtn");
      const copyAnswerBtn = document.getElementById("copyAnswerBtn");
      const chatSection = document.getElementById("chatSection");
      const messageInput = document.getElementById("messageInput");
      const receivedMessagesDiv = document.getElementById("receivedMessages");
      const sendButton = document.getElementById("sendMessageButton");

      let pc; // RTCPeerConnection
      let dataChannel; // Will be set when the sender's data channel arrives

      function setStatus(msg) {
        statusDiv.textContent = "Status: " + msg;
        console.log("[Receiver]", msg);
      }

      // ========== Step 1: Set Offer & Create Answer ==========
      setOfferBtn.onclick = async () => {
        try {
          const offer = JSON.parse(offerInput.value);
          setStatus("Creating peer connection...");

          // Same STUN servers as sender
          pc = new RTCPeerConnection({
            iceServers: [
              { urls: "stun:stun.l.google.com:19302" },
              { urls: "stun:stun1.l.google.com:19302" },
            ],
          });

          // === Handle incoming data channel from sender ===
          pc.ondatachannel = (event) => {
            setStatus("Data channel received!");
            dataChannel = event.channel;

            dataChannel.onopen = () => {
              setStatus("Data channel OPEN! You can chat now.");
              chatSection.style.display = "block";
            };
            dataChannel.onclose = () => setStatus("Data channel closed.");
            dataChannel.onmessage = (event) => {
              receivedMessagesDiv.innerHTML += `<p class="received">Sender: ${event.data}</p>`;
            };
          };

          // === ICE Candidate Handling ===
          pc.onicecandidate = (event) => {
            if (event.candidate) {
              console.log("ICE candidate found:", event.candidate.candidate);
            } else {
              // All candidates gathered — the full answer is ready
              setStatus(
                "ICE gathering complete. Copy the answer below and paste it in the Sender page.",
              );
              answerOutput.value = JSON.stringify(pc.localDescription);
              copyAnswerBtn.disabled = false;
            }
          };

          pc.oniceconnectionstatechange = () => {
            const state = pc.iceConnectionState;
            setStatus("ICE connection state: " + state);
            if (state === "failed" || state === "disconnected") {
              document.getElementById("troubleshoot").style.display = "block";
            }
            if (state === "connected" || state === "completed") {
              document.getElementById("troubleshoot").style.display = "none";
            }
          };

          // Set the remote description (offer from sender)
          await pc.setRemoteDescription(new RTCSessionDescription(offer));
          setStatus("Offer set. Creating answer...");

          // Create and set local description (answer)
          const answer = await pc.createAnswer();
          await pc.setLocalDescription(answer);
          setStatus(
            "Answer created. Waiting for ICE candidates to be gathered...",
          );
        } catch (e) {
          setStatus("Error: " + e.message);
        }
      };

      // Copy answer to clipboard (with fallback for Brave / file:// contexts)
      copyAnswerBtn.onclick = () => {
        copyToClipboard(answerOutput.value);
        setStatus("Answer copied! Now paste it in the Sender page.");
      };

      function copyToClipboard(text) {
        if (navigator.clipboard && window.isSecureContext) {
          navigator.clipboard.writeText(text).catch(() => fallbackCopy(text));
        } else {
          fallbackCopy(text);
        }
      }

      function fallbackCopy(text) {
        const ta = document.createElement("textarea");
        ta.value = text;
        ta.style.position = "fixed";
        ta.style.opacity = "0";
        document.body.appendChild(ta);
        ta.select();
        document.execCommand("copy");
        document.body.removeChild(ta);
      }

      // ========== Step 3: Send Messages ==========
      sendButton.onclick = () => {
        const message = messageInput.value.trim();
        if (!message) return;
        if (!dataChannel || dataChannel.readyState !== "open") {
          setStatus("Data channel not open yet!");
          return;
        }
        dataChannel.send(message);
        receivedMessagesDiv.innerHTML += `<p class="sent">You: ${message}</p>`;
        messageInput.value = "";
      };

      // Send on Enter key
      messageInput.addEventListener("keydown", (e) => {
        if (e.key === "Enter" && !e.shiftKey) {
          e.preventDefault();
          sendButton.click();
        }
      });

      setStatus("Waiting for offer. Paste it above.");
    </script>

    <footer>
      Built by
      <a
        href="https://arifulislamat.com"
        target="_blank"
        rel="noopener noreferrer"
        >Ariful Islam</a
      >
      · WebRTC Learning Playground
    </footer>
  </body>
</html>