DataChannel on Android only opens on one side

[Cyrill]

Hi,

I'm trying to get a DataChannel between two Android devices. Chrome and Firefox to Android works really good but I'm running into this when trying it between two Android devices:

I tested this between a Nexus 5 and a Nexus 7 (2012) over a strong WLAN conneciton.

On the offerer side the dataChannel.state never gets set to DataChannel.State.OPEN. On the receiver end it does.

Some logs (DataChannelService is my service that creates the PeerConnection etc.)

offerer:

I/DataChannelService( 5639): IceConnectionState changed: CONNECTED

I/DataChannelService( 5639): Ice Connection complete, registering Observers

I/DataChannelService( 5639): IceConnectionState changed: COMPLETED

I/libjingle( 5639): Channel socket writable (data, 1) for the first time

I/libjingle( 5639): Using Cand[2702239670:1:udp:2122129151:192.168.1.103:41326:local::0:ONTsw7w84B7WuzBc:jc4ItFqNg1IsBT2

yd52kRsBs]->Cand[3467446226:1:udp:2122129151:192.168.1.109:60366:local::0:W7sBpQ0vV8TC/Y0t:COSc71Ot9jtyzDOSOrC7U/wx]

I/libjingle( 5639): Changing data state, recv=1 send=1

I/libjingle( 5639): Sent CONTROL message on channel 1

I/libjingle( 5639): DataChannel received OPEN_ACK message, sid = 1

... 

peer/receiver:

 

I/DataChannelService(26746): IceConnectionState changed: CONNECTED

I/DataChannelService(26746): Ice Connection complete, registering Observers

I/libjingle(26746): Channel socket writable (data, 1) for the first time

I/libjingle(26746): Using Cand[3467446226:1:udp:2122129151:192.168.1.109:60366:local::0:W7sBpQ0vV8TC/Y0t:COSc71Ot9jtyzDO

SOrC7U/wx]->Cand[2702239670:1:udp:2122129151:192.168.1.103:41326:local::0:ONTsw7w84B7WuzBc:jc4ItFqNg1IsBT2yd52kRsBs]

I/libjingle(26746): Changing data state, recv=1 send=1

I/DataChannelService(26746): PeerConnection onDataChannel State: CONNECTING

I/libjingle(26746): Sent CONTROL message on channel 1

I/DataChannelService(26746): DataChannel state changed: OPEN

As you can see the offerer gets a writable socket but the DataChannel never opens. On the peer the onDataChannel state changes are logged and the DataChannel opens.

I tried to send messages between them after this but in neither direction anything arrives.

I have tried to offer on both devices with the same results.

Any idea what is going on here?

[Jiayang Liu]

Is the offerer datachannel in "connecting" state? You may add more logging in DataChannel::UpdateState to see why it doesn't transition to OPEN.

Are you using an up-to-date webrtc checkout?

[Cyrill]

I just realised that on the offerer side the datachannel never gets created as onDataChannel doesn't fire. I'm calling peerConnection.createDataChannel on the offerer and I figured that should trigger onDataChannel.

I updated and built libjingle last tuesday.

[Jiayang Liu]

The offerer DataChannel reference is returned from offerer.createDataChannel, not from onDataChannel. 

OnDataChannel is only called on the remote side not calling createDataChannel.

[Cyrill]

Ah, that makes sense. It's working great now, thanks!

But is there some documentation about DataChannels with libjingle? I feel like I have the guess a lot of things here...

[Jiayang Liu]

If you are familiar with the JS API (http://dev.w3.org/2011/webrtc/editor/webrtc.html), it's fairly straight forward to map it to the C++ API.

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[Gilded Honour]

So what side should I call createDataChannel on:  "offer" or "answer" 's?