Fix: Use ondatachannel instead of createDataChannel for answerer

CRITICAL BUG FIX: As the answerer, we should NOT create our own data channel.
The host (offerer) creates the channel, and we receive it via ondatachannel event.

This was causing messages to be sent on a different channel than the one
the host was listening to, so no messages were being received.

Changes:
- Remove pc.createDataChannel() call
- Add pc.ondatachannel event handler
- Wrap data channel setup in setupDataChannel() function
- Called when channel is received from host

test-connect.js

@@ -82,84 +82,88 @@ async function main() {
     console.log('\n3. Creating WebRTC peer connection...')
     const pc = new RTCPeerConnection(RTC_CONFIG)
 
-    // 4. Create data channel
-    console.log('4. Creating data channel...')
-    const dc = pc.createDataChannel('chat')
-
-    // Set up data channel handlers
+    // 4. Wait for data channel (we're the answerer, host creates the channel)
+    console.log('4. Waiting for data channel from host...')
+    let dc = null
     let identified = false
 
-    dc.onopen = () => {
-      console.log('   ✓ Data channel opened!')
-      console.log(`   Data channel state: ${dc.readyState}`)
+    // Function to setup data channel handlers
+    const setupDataChannel = (channel) => {
+      dc = channel
 
-      // Longer delay to ensure both sides are ready
-      setTimeout(() => {
-        console.log(`   Data channel state before send: ${dc.readyState}`)
-        if (dc.readyState !== 'open') {
-          console.error(`   ❌ Data channel not open: ${dc.readyState}`)
-          return
+      dc.onopen = () => {
+        console.log('   ✓ Data channel opened!')
+        console.log(`   Data channel state: ${dc.readyState}`)
+
+        // Longer delay to ensure both sides are ready
+        setTimeout(() => {
+          console.log(`   Data channel state before send: ${dc.readyState}`)
+          if (dc.readyState !== 'open') {
+            console.error(`   ❌ Data channel not open: ${dc.readyState}`)
+            return
+          }
+
+          // Send identify message (demo protocol)
+          console.log(`📤 Sending identify message...`)
+          const identifyMsg = JSON.stringify({
+            type: 'identify',
+            from: rondevu.getUsername()
+          })
+          console.log(`   Message:`, identifyMsg)
+          dc.send(identifyMsg)
+          console.log(`   ✓ Identify message sent, bufferedAmount: ${dc.bufferedAmount}`)
+        }, 500)
+      }
+
+      dc.onclose = () => {
+        console.log('   ❌ Data channel closed!')
+      }
+
+      dc.onmessage = (event) => {
+        console.log(`📥 RAW DATA:`, event.data)
+        try {
+          const msg = JSON.parse(event.data)
+          console.log(`📥 Parsed message:`, JSON.stringify(msg, null, 2))
+
+          if (msg.type === 'identify_ack' && !identified) {
+            identified = true
+            console.log(`✅ Connection acknowledged by @${msg.from}`)
+
+            // Now send the actual chat message
+            console.log(`📤 Sending chat message: "${MESSAGE}"`)
+            dc.send(JSON.stringify({
+              type: 'message',
+              text: MESSAGE
+            }))
+
+            // Keep connection open longer to see if we get a response
+            setTimeout(() => {
+              console.log('\n✅ Test completed successfully!')
+              dc.close()
+              pc.close()
+              process.exit(0)
+            }, 5000)
+          } else if (msg.type === 'message') {
+            console.log(`💬 @${msg.from || 'peer'}: ${msg.text}`)
+          } else {
+            console.log(`📥 Unknown message type: ${msg.type}`)
+          }
+        } catch (err) {
+          console.log(`📥 Parse error:`, err.message)
+          console.log(`📥 Raw data was:`, event.data)
         }
+      }
 
-        // Send identify message (demo protocol)
-        console.log(`📤 Sending identify message...`)
-        const identifyMsg = JSON.stringify({
-          type: 'identify',
-          from: rondevu.getUsername()
-        })
-        console.log(`   Message:`, identifyMsg)
-        dc.send(identifyMsg)
-        console.log(`   ✓ Identify message sent, bufferedAmount: ${dc.bufferedAmount}`)
-      }, 500)
-    }
-
-    dc.onclose = () => {
-      console.log('   ❌ Data channel closed!')
-    }
-
-    dc.onerror = (error) => {
-      console.error('❌ Data channel error:', error)
-      process.exit(1)
-    }
-
-    dc.onmessage = (event) => {
-      console.log(`📥 RAW DATA:`, event.data)
-      try {
-        const msg = JSON.parse(event.data)
-        console.log(`📥 Parsed message:`, JSON.stringify(msg, null, 2))
-
-        if (msg.type === 'identify_ack' && !identified) {
-          identified = true
-          console.log(`✅ Connection acknowledged by @${msg.from}`)
-
-          // Now send the actual chat message
-          console.log(`📤 Sending chat message: "${MESSAGE}"`)
-          dc.send(JSON.stringify({
-            type: 'message',
-            text: MESSAGE
-          }))
-
-          // Keep connection open longer to see if we get a response
-          setTimeout(() => {
-            console.log('\n✅ Test completed successfully!')
-            dc.close()
-            pc.close()
-            process.exit(0)
-          }, 5000)
-        } else if (msg.type === 'message') {
-          console.log(`💬 @${msg.from || 'peer'}: ${msg.text}`)
-        } else {
-          console.log(`📥 Unknown message type: ${msg.type}`)
-        }
-      } catch (err) {
-        console.log(`📥 Parse error:`, err.message)
-        console.log(`📥 Raw data was:`, event.data)
+      dc.onerror = (error) => {
+        console.error('❌ Data channel error:', error)
+        process.exit(1)
       }
     }
 
-    dc.onerror = (error) => {
-      console.error('❌ Data channel error:', error)
-      process.exit(1)
+    // Receive data channel from host (we're the answerer)
+    pc.ondatachannel = (event) => {
+      console.log('   ✓ Data channel received from host!')
+      setupDataChannel(event.channel)
     }
 
     // 5. Set up ICE candidate exchange FIRST