failed to use RTCDataChannel to send message

[gaox...@foxmail.com]

 I have already managed to share video and audio between peers however i can't find a way to send message between peers using RTCDataChannel. i guess the problem is that 

- (void)peerConnection:(RTCPeerConnection*)peerConnection
    didOpenDataChannel:(RTCDataChannel*)dataChannel

is never called.what puzzled me is that RTCDataChannel state can changed to kRTCDataChannelStateOpen

- (void)channelDidChangeState:(RTCDataChannel*)channel{
    NSLog(@"did change state %d",channel.state);
}

and sendData return Yes

if([_rtcChannel sendData:buffer]){
     NSLog(@"send msg");//_rtcChannel was created before creating offer
}

Questions:

1. When didOpenDataChannel will be called?
2. How to send message between peers using RTCDataChannel?

[Taylor Brandstetter]

I've seen this kind of question a lot, so I created a question/answer on StackOverflow that tries to explain how the whole data channel negotiation model works: http://stackoverflow.com/questions/43788872/how-are-data-channels-negotiated-between-two-peers-in-webrtc/43788873

Does this answer your questions?

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[Archer Chen]

Hi, taylor

Thank for your answer.

I am try to create data channel using your explanation.

In web<chrome Version 58.0.3029.96 (64-bit)>,  in myrtclib.js I set up the 

    var data_constraint = {reliable :false};

    function createDataChannel(role) {

        try {

            sendDChannel = pc.createDataChannel("datachannel_"+room+role, data_constraint);

        } catch (e) {

            console.log('error creating data channel ' + e);

            return;

        }

        sendDChannel.onopen = onSendChannelStateChange;

        sendDChannel.onclose = onSendChannelStateChange;

    }

In my iOS client, I set up the 'RTCDataChannelConfiguration'

- (RTCConfiguration *)peerConnectionConfiguration

{

    RTCConfiguration * configuration = [[RTCConfiguration alloc] init];

    

    if (!mICEServers)

    {

        mICEServers = [NSMutableArray array];

        NSArray * iceServers = @[RTCSTUNServerURL];  // RTCSTUNServerURL = @"stun:stun.l.google.com:19302";

        [mICEServers addObject:[self defaultSTUNServer:iceServers]];

    }

    

    configuration.iceServers = mICEServers;

    return configuration;

}

- (RTCMediaConstraints *)peerConnectionMediaConstraints

{

    return [[RTCMediaConstraints alloc] initWithMandatoryConstraints:nil optionalConstraints:nil];

}

- (RTCPeerConnection *)createPeerConnectionWithDataChannelLabel:(NSString *)connectionId

{

    RTCConfiguration * configuration = [self peerConnectionConfiguration];

    RTCMediaConstraints * mediaConstraints = [self peerConnectionMediaConstraints];

    

    RTCPeerConnection * peerConnection = [mPeerFactory peerConnectionWithConfiguration:configuration constraints:mediaConstraints delegate:self];

    

    if (peerConnection)

    {

        NSLog(@"Create peer connection successfully for %@", connectionId);

        

        RTCDataChannelConfiguration * dataChannelConfiguration = [[RTCDataChannelConfiguration alloc] init];

        dataChannelConfiguration.channelId = 10000;

        dataChannelConfiguration.isNegotiated = YES;

        // connectionId keep the same with js <format : [NSString stringWithFormat:@"datachannel_%@caller", roomName]>

        RTCDataChannel *dataChannel = [peerConnection dataChannelForLabel:connectionId configuration:dataChannelConfiguration];

        

        if (dataChannel)

        {

            dataChannel.delegate = self;

            NSLog(@"Data channel status : %@", [dataChannel readyStatus]);

        }

        else

        {

            NSLog(@"Create data channel failed for %@", connectionId);

        }

    }

    else

    {

        NSLog(@"Create peer connection failed for %@", connectionId);

    }

    return peerConnection;

}

Now, issue is app crash when run to dataChannelForLabel:configuration: ?
If I don't set up the isNegotiated and channelId of dataChannelConfiguration in here, where can I set it? The property of RTCDataChannel is readonly.

Device info:

My mac: 10.12.4

xcode : 8.3.2

WebRTC framework verson: M58

git status

HEAD detached at 4e72b0f87

在 2017年5月5日星期五 UTC+8上午1:07:38，Taylor Brandstetter写道：

I've seen this kind of question a lot, so I created a question/answer on StackOverflow that tries to explain how the whole data channel negotiation model works: http://stackoverflow.com/questions/43788872/how-are-data-channels-negotiated-between-two-peers-in-webrtc/43788873

Does this answer your questions?

On Wed, May 3, 2017 at 7:14 AM, <gaox...@foxmail.com> wrote:

 I have already managed to share video and audio between peers however i can't find a way to send message between peers using RTCDataChannel. i guess the problem is that 

- (void)peerConnection:(RTCPeerConnection*)peerConnection
    didOpenDataChannel:(RTCDataChannel*)dataChannel

is never called.what puzzled me is that RTCDataChannel state can changed to kRTCDataChannelStateOpen

- (void)channelDidChangeState:(RTCDataChannel*)channel{
    NSLog(@"did change state %d",channel.state);
}

and sendData return Yes

if([_rtcChannel sendData:buffer]){
     NSLog(@"send msg");//_rtcChannel was created before creating offer
}

Questions:

1. When didOpenDataChannel will be called?
2. How to send message between peers using RTCDataChannel?

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[Archer Chen]

var data_constraint = {negotiated : true, id : 10000};

Setting is here.


在 2017年5月5日星期五 UTC+8上午10:55:47，Archer Chen写道：

[Taylor Brandstetter]

The crash is tracked by this bug I never got around to fixing: https://bugs.chromium.org/p/webrtc/issues/detail?id=4619

But the real issue here is the is the channelId of 10000. I forgot to mention this, but the ID isn't just an arbitrary value; it's a 0-based SCTP stream ID, and it can only go as high as the number of negotiated SCTP streams. Which will be 1024 by default for Chrome, so 10000 is too high. I'll update the SO question to call this out.

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[Archer Chen]

@Taylor,

Thank you for your reply. Now it works, when the channelId is less than 1024. Thank you very much.

在 2017年5月5日星期五 UTC+8下午4:16:17，Taylor Brandstetter写道：

[gaox...@foxmail.com]

Thank you very much.

On Friday, May 5, 2017 at 1:07:38 AM UTC+8, Taylor Brandstetter wrote:

I've seen this kind of question a lot, so I created a question/answer on StackOverflow that tries to explain how the whole data channel negotiation model works: http://stackoverflow.com/questions/43788872/how-are-data-channels-negotiated-between-two-peers-in-webrtc/43788873

Does this answer your questions?

On Wed, May 3, 2017 at 7:14 AM, <gaox...@foxmail.com> wrote:

 I have already managed to share video and audio between peers however i can't find a way to send message between peers using RTCDataChannel. i guess the problem is that 

- (void)peerConnection:(RTCPeerConnection*)peerConnection
    didOpenDataChannel:(RTCDataChannel*)dataChannel

is never called.what puzzled me is that RTCDataChannel state can changed to kRTCDataChannelStateOpen

- (void)channelDidChangeState:(RTCDataChannel*)channel{
    NSLog(@"did change state %d",channel.state);
}

and sendData return Yes

if([_rtcChannel sendData:buffer]){
     NSLog(@"send msg");//_rtcChannel was created before creating offer
}

Questions:

1. When didOpenDataChannel will be called?
2. How to send message between peers using RTCDataChannel?

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