From 035e24977d6d5ad0a3887d5ae71098a556b95b9c Mon Sep 17 00:00:00 2001
From: rku-21 <rahul.k.upadhyay21@gmail.com>
Date: Wed, 6 May 2026 13:31:07 +0530
Subject: [PATCH] Queue ICE candidates until remoteDescription is set

---
 public/js/client.js | 56 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/public/js/client.js b/public/js/client.js
index 65cc3e9e..3303fb2f 100644
--- a/public/js/client.js
+++ b/public/js/client.js
@@ -625,6 +625,33 @@ let chatDataChannels = {}; // keep track of our peer chat data channels
 let fileDataChannels = {}; // keep track of our peer file sharing data channels
 let allPeers = {}; // keep track of all peers in the room, indexed by peer_id == socket.io id
 
+
+let pendingIceCandidates = {}; 
+
+function queueIceCandidate(peer_id, ice_candidate) {
+    if (!peer_id || !ice_candidate) return;
+    if (!pendingIceCandidates[peer_id]) pendingIceCandidates[peer_id] = [];
+    pendingIceCandidates[peer_id].push(ice_candidate);
+}
+
+async function flushIceCandidates(peer_id) {
+    const pc = peerConnections[peer_id];
+    const queued = pendingIceCandidates[peer_id];
+
+    if (!pc || !queued || queued.length === 0) return;
+    if (!pc.remoteDescription || !pc.remoteDescription.type) return;
+
+    delete pendingIceCandidates[peer_id];
+
+    for (const ice of queued) {
+        try {
+            await pc.addIceCandidate(new RTCIceCandidate(ice));
+        } catch (err) {
+            console.error('[Error] addIceCandidate (queued)', err);
+        }
+    }
+}
+
 let lastStats = null;
 
 // stream
@@ -2715,6 +2742,9 @@ async function handleAddPeer(config) {
     const peerConnection = new RTCPeerConnection({ iceServers: iceServers });
     peerConnections[peer_id] = peerConnection;
 
+    // If ICE arrived before we processed addPeer, keep it and flush when ready.
+    flushIceCandidates(peer_id).catch((err) => console.error('[Error] flushIceCandidates', err));
+
     allPeers = peers;
     // Ensure extras object exists for every peer to avoid undefined checks later
     try {
@@ -3115,10 +3145,19 @@ function handleSessionDescription(config) {
 
     const pc = peerConnections[peer_id];
 
+    if (!pc) {
+        console.warn('[RTCSessionDescription] peer connection missing, ignoring', { peer_id });
+        return;
+    }
+
     // https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection/setRemoteDescription
     pc.setRemoteDescription(remote_description)
         .then(() => {
             console.log('setRemoteDescription done!');
+
+            // Drain any queued ICE now that remoteDescription is set.
+            flushIceCandidates(peer_id).catch((err) => console.error('[Error] flushIceCandidates', err));
+
             if (session_description.type == 'offer') {
                 console.log('Creating answer');
                 // https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection/createAnswer
@@ -3166,7 +3205,20 @@ function handleSessionDescription(config) {
 function handleIceCandidate(config) {
     const { peer_id, ice_candidate } = config;
     // https://developer.mozilla.org/en-US/docs/Web/API/RTCIceCandidate
-    peerConnections[peer_id].addIceCandidate(new RTCIceCandidate(ice_candidate)).catch((err) => {
+    const pc = peerConnections[peer_id];
+
+    if (!pc) {
+        queueIceCandidate(peer_id, ice_candidate);
+        return;
+    }
+
+    // Queue until remoteDescription is set; otherwise addIceCandidate can fail and the candidate is lost.
+    if (!pc.remoteDescription || !pc.remoteDescription.type) {
+        queueIceCandidate(peer_id, ice_candidate);
+        return;
+    }
+
+    pc.addIceCandidate(new RTCIceCandidate(ice_candidate)).catch((err) => {
         console.error('[Error] addIceCandidate', err);
     });
 }
@@ -3229,6 +3281,7 @@ function handleDisconnect(reason) {
     chatDataChannels = {};
     fileDataChannels = {};
     peerConnections = {};
+    pendingIceCandidates = {};
     peerScreenMediaElements = {};
     peerVideoMediaElements = {};
     peerAudioMediaElements = {};
@@ -3302,6 +3355,7 @@ function handleRemovePeer(config) {
     delete chatDataChannels[peer_id];
     delete fileDataChannels[peer_id];
     delete peerConnections[peer_id];
+    delete pendingIceCandidates[peer_id];
     delete peerScreenMediaElements[peerScreenId];
     delete peerVideoMediaElements[peerVideoId];
     delete peerAudioMediaElements[peerAudioId];