Add credentialed TURN server handling and update RTC configuration to gather direct, STUN, and TURN candidates. Enhance peer connection management with new credentials parameter.

www/js/main.js

@@ -14,9 +14,8 @@
 
 const $self = {
   rtcConfig: {
-    // WebRTC has no "STUN-only" transport policy. Using `all` with only
-    // STUN servers configured allows host and server-reflexive candidates,
-    // while ensuring that no TURN relay candidate can be created.
+    // Gather direct, STUN, and TURN candidates. ICE prefers direct/STUN
+    // candidate pairs and falls back to TURN when those checks fail.
     iceTransportPolicy: 'all',
     iceServers: [
       { urls: 'stun:stun.l.google.com:19302' },
@@ -629,10 +628,15 @@ function handleScConnect() {
   console.log(`Self ID: ${$self.id}`);
 }
 
-function handleScConnectedPeers({ peers }) {
+function handleScConnectedPeers({ peers, credentials }) {
   const ids = peers;
   console.log(`Connected peer IDs: ${ids.join(', ')}`);
 
+  addCredentialedTurnServer([
+    'turn:182.92.86.220:3478?transport=udp',
+    'turn:182.92.86.220:3478?transport=tcp',
+  ], credentials);
+
   for (let id of ids) {
     if (id === $self.id) continue;
     // be polite with already-connected peers
@@ -736,6 +740,29 @@ async function handleScSignal({ sender,
  *  Utility Functions
  */
 
+function addCredentialedTurnServer(server_urls, { username, password }) {
+  // Add TURN after the STUN entries. ICE will still gather all candidate
+  // types, but direct and server-reflexive pairs have higher priority than
+  // relayed pairs under the standard ICE candidate priority rules.
+  const turn_server = {
+    urls: server_urls,
+    username: username,
+    credential: password,
+  };
+
+  const existing_index = $self.rtcConfig.iceServers.findIndex(server =>
+    Array.isArray(server.urls)
+      && server.urls.some(url => server_urls.includes(url)));
+
+  // Refresh the expiring credentials when the signaling channel reconnects
+  // instead of accumulating duplicate TURN entries.
+  if (existing_index >= 0) {
+    $self.rtcConfig.iceServers[existing_index] = turn_server;
+  } else {
+    $self.rtcConfig.iceServers.push(turn_server);
+  }
+}
+
 function prepareNamespace(hash, set_location) {
   let ns = hash.replace(/^#/, ''); // remove # from the hash
   if (/^[a-z]{4}-[a-z]{4}-[a-z]{4}$/.test(ns)) {