Fix critical bug: track and use data channels from offers

This fixes the root cause of all connection failures. The service pool
was creating data channels but discarding the references, then trying
to wait for a 'datachannel' event that would never fire.

Changes:
- Add dataChannel tracking to OfferPool and ServicePool
- Save data channel references when creating offers
- Pass channels through the answer flow
- Use the existing channel instead of waiting for an event
- Wait for channel.onopen instead of ondatachannel

The offerer (service pool) creates the data channel and must keep that
reference. The 'ondatachannel' event only fires on the answerer side.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/service-pool.ts

@@ -138,11 +138,13 @@ export class ServicePool {
     // 2. Create additional offers for pool (poolSize - 1)
     const additionalOffers: Offer[] = [];
     const additionalPeerConnections: RTCPeerConnection[] = [];
+    const additionalDataChannels: RTCDataChannel[] = [];
     if (poolSize > 1) {
       try {
         const result = await this.createOffers(poolSize - 1);
         additionalOffers.push(...result.offers);
         additionalPeerConnections.push(...result.peerConnections);
+        additionalDataChannels.push(...result.dataChannels);
       } catch (error) {
         this.handleError(error as Error, 'initial-offer-creation');
       }
@@ -157,7 +159,7 @@ export class ServicePool {
       onError: (err, ctx) => this.handleError(err, ctx)
     });
 
-    // Add all offers to pool with their peer connections
+    // Add all offers to pool with their peer connections and data channels
     const allOffers = [
       { id: service.offerId, peerId: this.credentials.peerId, sdp: service.offerSdp, topics: [], expiresAt: service.expiresAt, lastSeen: Date.now() },
       ...additionalOffers
@@ -166,7 +168,11 @@ export class ServicePool {
       service.peerConnection,
       ...additionalPeerConnections
     ];
-    await this.offerPool.addOffers(allOffers, allPeerConnections);
+    const allDataChannels = [
+      service.dataChannel,
+      ...additionalDataChannels
+    ];
+    await this.offerPool.addOffers(allOffers, allPeerConnections, allDataChannels);
 
     // 4. Start polling
     await this.offerPool.start();
@@ -296,33 +302,32 @@ export class ServicePool {
         sdp: answer.sdp
       });
 
-      // Wait for data channel (answerer creates it, we receive it)
-      const channel = await new Promise<RTCDataChannel>((resolve, reject) => {
-        const timeout = setTimeout(
-          () => reject(new Error('Timeout waiting for data channel')),
-          30000
-        );
+      // Use the data channel we created when making the offer
+      if (!answer.dataChannel) {
+        throw new Error('No data channel found for answered offer');
+      }
 
-        peer.on('datachannel', (ch: RTCDataChannel) => {
-          clearTimeout(timeout);
-          resolve(ch);
+      const channel = answer.dataChannel;
+
+      // Wait for the channel to open (it was created when we made the offer)
+      if (channel.readyState !== 'open') {
+        await new Promise<void>((resolve, reject) => {
+          const timeout = setTimeout(
+            () => reject(new Error('Timeout waiting for data channel to open')),
+            30000
+          );
+
+          channel.onopen = () => {
+            clearTimeout(timeout);
+            resolve();
+          };
+
+          channel.onerror = (error) => {
+            clearTimeout(timeout);
+            reject(new Error('Data channel error'));
+          };
         });
-
-        // Also check if channel already exists
-        if (peer.pc.ondatachannel) {
-          const existingHandler = peer.pc.ondatachannel;
-          peer.pc.ondatachannel = (event) => {
-            clearTimeout(timeout);
-            resolve(event.channel);
-            if (existingHandler) existingHandler.call(peer.pc, event);
-          };
-        } else {
-          peer.pc.ondatachannel = (event) => {
-            clearTimeout(timeout);
-            resolve(event.channel);
-          };
-        }
-      });
+      }
 
       // Register connection
       this.connections.set(connectionId, {
@@ -366,15 +371,16 @@ export class ServicePool {
   /**
    * Create multiple offers
    */
-  private async createOffers(count: number): Promise<{ offers: Offer[], peerConnections: RTCPeerConnection[] }> {
+  private async createOffers(count: number): Promise<{ offers: Offer[], peerConnections: RTCPeerConnection[], dataChannels: RTCDataChannel[] }> {
     if (count <= 0) {
-      return { offers: [], peerConnections: [] };
+      return { offers: [], peerConnections: [], dataChannels: [] };
     }
 
     // Server supports max 10 offers per request
     const batchSize = Math.min(count, 10);
     const offers: Offer[] = [];
     const peerConnections: RTCPeerConnection[] = [];
+    const dataChannels: RTCDataChannel[] = [];
 
     try {
       // Create peer connections and generate offers
@@ -384,8 +390,9 @@ export class ServicePool {
           iceServers: [{ urls: 'stun:stun.l.google.com:19302' }]
         });
 
-        // Create data channel (required for offers)
-        pc.createDataChannel('rondevu-service');
+        // Create data channel (required for offers) and save reference
+        const channel = pc.createDataChannel('rondevu-service');
+        dataChannels.push(channel);
 
         // Create offer
         const offer = await pc.createOffer();
@@ -418,7 +425,7 @@ export class ServicePool {
       throw error;
     }
 
-    return { offers, peerConnections };
+    return { offers, peerConnections, dataChannels };
   }
 
   /**
@@ -431,6 +438,7 @@ export class ServicePool {
     offerSdp: string;
     expiresAt: number;
     peerConnection: RTCPeerConnection;
+    dataChannel: RTCDataChannel;
   }> {
     const { username, privateKey, serviceFqn, rtcConfig, isPublic, metadata, ttl } = this.options;
 
@@ -439,7 +447,7 @@ export class ServicePool {
       iceServers: [{ urls: 'stun:stun.l.google.com:19302' }]
     });
 
-    pc.createDataChannel('rondevu-service');
+    const dataChannel = pc.createDataChannel('rondevu-service');
 
     // Create offer
     const offer = await pc.createOffer();
@@ -491,7 +499,8 @@ export class ServicePool {
       offerId: data.offerId,
       offerSdp,
       expiresAt: data.expiresAt,
-      peerConnection: pc // Keep peer connection alive
+      peerConnection: pc, // Keep peer connection alive
+      dataChannel // Keep data channel alive
     };
   }
 
@@ -504,7 +513,7 @@ export class ServicePool {
     }
 
     const result = await this.createOffers(count);
-    await this.offerPool.addOffers(result.offers, result.peerConnections);
+    await this.offerPool.addOffers(result.offers, result.peerConnections, result.dataChannels);
     this.updateStatus();
   }