Android: Crash with NullpointerException when attempting to init call

[komaxx]

On my Samsung A15 device, when I attempt to init an audio-only SIP call, I run into this exception:

03-21 16:31:05.647 E AndroidRuntime: java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.List org.webrtc.PeerConnection.getTransceivers()' on a null object reference
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.PeerConnectionObserver.getTransceiversTrack(SourceFile:13)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.MethodCallHandlerImpl.getTrackForId(SourceFile:65)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.MethodCallHandlerImpl.getNextTrackUUID(SourceFile:10)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.GetUserMediaImpl.getUserAudio(SourceFile:66)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.GetUserMediaImpl.getUserMedia(SourceFile:17)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.GetUserMediaImpl.access$100(SourceFile:1)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.GetUserMediaImpl$2.invoke(SourceFile:14)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.GetUserMediaImpl.lambda$requestPermissions$0(SourceFile:66)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.GetUserMediaImpl.a(SourceFile:1)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.c.invoke(SourceFile:1)
03-21 16:31:05.647 E AndroidRuntime: 	at com.cloudwebrtc.webrtc.utils.PermissionUtils$1.onReceiveResult(SourceFile:15)
03-21 16:31:05.647 E AndroidRuntime: 	at android.os.ResultReceiver$MyRunnable.run(ResultReceiver.java:50)
03-21 16:31:05.647 E AndroidRuntime: 	at android.os.Handler.handleCallback(Handler.java:958)
03-21 16:31:05.647 E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:99)
03-21 16:31:05.647 E AndroidRuntime: 	at android.os.Looper.loopOnce(Looper.java:230)
03-21 16:31:05.647 E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:319)
03-21 16:31:05.647 E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:8919)
03-21 16:31:05.647 E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
03-21 16:31:05.647 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:578)
03-21 16:31:05.647 E AndroidRuntime: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1103)

Up until that point, everything looks good, the WebSocket connection is established, there are no warnings.
Here's the log up until the point of crash:

03-21 16:31:05.515 I org.webrtc.Logging: PeerConnectionFactory: PeerConnectionFactory was initialized without an injected Loggable. Any existing Loggable will be deleted.
03-21 16:31:05.515 D SemWifiApAdvancedAutohotspotService: prev history :10
03-21 16:31:05.528 D AudioFlinger: ro.audio.silent is ignored since no output device is set
03-21 16:31:05.528 D AudioFlinger: ro.audio.silent is ignored since no output device is set
03-21 16:31:05.542 I org.webrtc.Logging: WebRtcAudioManagerExternal: Sample rate is set to 48000 Hz
03-21 16:31:05.543 I org.webrtc.Logging: WebRtcAudioManagerExternal: Sample rate is set to 48000 Hz
03-21 16:31:05.543 I org.webrtc.Logging: JavaAudioDeviceModule: createAudioDeviceModule
03-21 16:31:05.543 I org.webrtc.Logging: JavaAudioDeviceModule: HW NS will be used.
03-21 16:31:05.543 I org.webrtc.Logging: JavaAudioDeviceModule: HW AEC will be used.
03-21 16:31:05.544 I org.webrtc.Logging: JavaAudioDeviceModule: Low latency mode will be used.
03-21 16:31:05.544 I org.webrtc.Logging: WebRtcAudioEffectsExternal: ctor@[name=main, id=2]
03-21 16:31:05.544 I org.webrtc.Logging: WebRtcAudioRecordExternal: ctor@[name=main, id=2]
03-21 16:31:05.544 I org.webrtc.Logging: WebRtcAudioTrackExternal: ctor@[name=main, id=2]
03-21 16:31:05.545 I org.webrtc.Logging: JavaAudioDeviceModule: setNoiseSuppressorEnabled: true
03-21 16:31:05.545 W org.webrtc.Logging: WebRtcAudioRecordExternal: SetNoiseSuppressorEnabled(true)
03-21 16:31:05.545 E org.webrtc.Logging: WebRtcAudioEffectsExternal: Attempting to enable or disable nonexistent NoiseSuppressor.
03-21 16:31:05.546 W AudioALSACaptureDataProviderNormal: readThread, latency_in_s,0.000000,0.039166,0.000034, totalTime 0.039200 > logTimeout 0.022000 TIMEOUT!!
03-21 16:31:05.547 D libMEOW : meow new tls: 0xb400007177e72a00
03-21 16:31:05.547 D libMEOW : applied 1 plugins for [ch.newvoice.mobicall.ng]:
03-21 16:31:05.547 D libMEOW :   plugin 1: [libMEOW_gift.so]: 0xb400007409b2da80
03-21 16:31:05.548 D libMEOW : rebuild call chain: 0xb400007177daafc0
03-21 16:31:05.548 I org.webrtc.Logging: EglBase14Impl: Using OpenGL ES version 2
03-21 16:31:05.586 W AudioALSACaptureDataProviderNormal: readThread, latency_in_s,0.000001,0.039607,0.000038, totalTime 0.039646 > logTimeout 0.022000 TIMEOUT!!
03-21 16:31:05.591 I GestureDetector: handleMessage TAP
03-21 16:31:05.592 I GestureDetector: handleMessage TAP
03-21 16:31:05.597 W AudioCapabilities: Unsupported mime audio/x-ima
03-21 16:31:05.597 W AudioCapabilities: Unsupported mime audio/mpeg-L1
03-21 16:31:05.597 W AudioCapabilities: Unsupported mime audio/mpeg-L2
03-21 16:31:05.597 W VideoCapabilities: Unsupported mime video/wvc1
03-21 16:31:05.597 W VideoCapabilities: Unsupported mime video/x-ms-wmv
03-21 16:31:05.597 W AudioCapabilities: Unsupported mime audio/x-adpcm-dvi-ima
03-21 16:31:05.597 W AudioCapabilities: Unsupported mime audio/x-adpcm-dvi-ima
03-21 16:31:05.597 W AudioCapabilities: Unsupported mime audio/x-adpcm-ms
03-21 16:31:05.597 W AudioCapabilities: Unsupported mime audio/x-adpcm-ms
03-21 16:31:05.599 W VideoCapabilities: Unrecognized profile/level 32768/256 for video/mp4v-es
03-21 16:31:05.600 W VideoCapabilities: Unsupported mime image/vnd.android.heic
03-21 16:31:05.600 W VideoCapabilities: Unsupported mime image/vnd.android.heic
03-21 16:31:05.600 W VideoCapabilities: Unsupported mime image/vnd.android.heic
03-21 16:31:05.600 W VideoCapabilities: Unsupported mime image/vnd.android.heic
03-21 16:31:05.601 W VideoCapabilities: Unrecognized profile/level 32768/256 for video/mp4v-es
03-21 16:31:05.601 W VideoCapabilities: Unrecognized profile/level 32768/256 for video/mp4v-es
03-21 16:31:05.623 I org.webrtc.Logging: WebRtcAudioRecordExternal: enableBuiltInAEC(true)
03-21 16:31:05.623 I org.webrtc.Logging: WebRtcAudioEffectsExternal: setAEC(true)
03-21 16:31:05.623 I org.webrtc.Logging: WebRtcAudioRecordExternal: enableBuiltInNS(true)
03-21 16:31:05.623 I org.webrtc.Logging: WebRtcAudioEffectsExternal: setNS(true)
03-21 16:31:05.624 I org.webrtc.Logging: PeerConnectionFactory: onSignalingThreadReady
03-21 16:31:05.624 I org.webrtc.Logging: PeerConnectionFactory: onWorkerThreadReady
03-21 16:31:05.625 I org.webrtc.Logging: PeerConnectionFactory: onNetworkThreadReady
03-21 16:31:05.626 W AudioALSACaptureDataProviderNormal: readThread, latency_in_s,0.000000,0.039345,0.000032, totalTime 0.039377 > logTimeout 0.022000 TIMEOUT!!
03-21 16:31:05.627 I hbox:interactor: Explicit concurrent mark compact GC freed 7587KB AllocSpace bytes, 0(0B) LOS objects, 49% free, 11MB/22MB, paused 374us,4.159ms total 227.482ms
03-21 16:31:05.627 W hbox:interactor: Reducing the number of considered missed Gc histogram windows from 166 to 100
03-21 16:31:05.640 I flutter : 16:31:05_640 D  SIP | emit "peerconnection" 
03-21 16:31:05.640 I flutter : 16:31:05_640 D  SIP | newRTCSession() 
03-21 16:31:05.640 I flutter : 16:31:05_640 D  SIP | newRTCSession => Instance of 'EventNewRTCSession' 
03-21 16:31:05.640 I flutter : 16:31:05_640 D  call: r31fjp5wnjzfa7ot2ttv8673216766: CallStateEnum.CALL_INITIATION. app -(OUTGOING)-> , state: CallStateEnum.CALL_INITIATION
03-21 16:31:05.644 I FlutterWebRTCPlugin: getUserMedia(audio): mandatory: [], optional: [googNoiseSuppression: true, googEchoCancellation: true, echoCancellation: true, googEchoCancellation2: true, googDAEchoCancellation: true]
03-21 16:31:05.644 D AndroidRuntime: Shutting down VM

To Reproduce
Not sure yet. Right now this only happens with my (rather complex) app and a not publicly reachable SIP / ICE server. I'll attempt to reproduce with a minimal project and see if I can make the server publicly available somehow.

My method to init the call seems straight-forward enough (at least to me) - but maybe there's something wrong here already?

    final settings = UaSettings();

    final url = 'wss://<redacted>';

    settings.transportType = TransportType.WS;
    settings.register = false;
    // No idea why this is required, there's no documentation. Some calls fail
    // though without setting this
    settings.sessionTimers = false;

    settings.webSocketUrl = url;

    settings.iceTransportPolicy = IceTransportPolicy.RELAY;
    settings.iceServers = _configuration.iceServers
        .map((ice) => {
              'urls': ice.url,
              'username': ice.username ?? '',
              'credential': ice.credential ?? '',
            })
        .toList(growable: false);
    settings.sessionTimersRefreshMethod = SipMethod.INVITE;

    settings.webSocketSettings.allowBadCertificate = true;

    settings.uri = 'sip:app@redacted.global';
    settings.authorizationUser = 'authUser';
    settings.password = 'password';
    settings.displayName = '<redacted>.App';

    settings.userAgent = 'Dart SIP Client v1.0.0';
    settings.dtmfMode = DtmfMode.RFC2833;

    _sipHelper.start(settings);

Expected behavior
Not crash ;)

Platform information

• Flutter version:

[✓] Flutter (Channel stable, 3.29.2, on macOS 15.3.2 24D81 darwin-arm64, locale en-US) [475ms]
    • Flutter version 3.29.2 on channel stable at /Users/matthiasschicker/dev/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision c236373904 (8 days ago), 2025-03-13 16:17:06 -0400
    • Engine revision 18b71d647a
    • Dart version 3.7.2
    • DevTools version 2.42.3

[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.1) [1,585ms]
    • Android SDK at /Users/matthiasschicker/Library/Android/sdk
    • Platform android-35, build-tools 35.0.1
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment (build 21.0.5+-12932927-b750.29)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 16.2) [943ms]
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 16C5032a
    • CocoaPods version 1.16.2

[✓] Chrome - develop for the web [8ms]
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2024.3) [7ms]
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 21.0.5+-12932927-b750.29)

[✓] VS Code (version 1.98.2) [7ms]
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension can be installed from:
      🔨 https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[✓] Connected device (5 available) [10.0s]
    • Pixel 8a (mobile)               • 49271JEKB10094            • android-arm64  • Android 15 (API 35)
    • MattPhone (wireless) (mobile)   • 00008030-000C551914E3802E • ios            • iOS 18.3.2 22D82
    • macOS (desktop)                 • macos                     • darwin-arm64   • macOS 15.3.2 24D81 darwin-arm64
    • Mac Designed for iPad (desktop) • mac-designed-for-ipad     • darwin         • macOS 15.3.2 24D81 darwin-arm64
    • Chrome (web)                    • chrome                    • web-javascript • Google Chrome 134.0.6998.118

[✓] Network resources [610ms]
    • All expected network resources are available.

• No issues found!

• Plugin version: sip_ua: 1.0.1, flutter_webrtc: 0.12.9
• OS: Android
• OS version: 13, 14, 15

[komaxx]

Did some more debugging, and found the following insights:

1. The crash is caused by this call on line 113 in PeerConnectionFactory.createPeerConnectionInternal responding with 0:

long nativePeerConnection = nativeCreatePeerConnection(this.nativeFactory, rtcConfig, constraints, nativeObserver, sslCertificateVerifier);

With that new PeerConnection object is created and subsequent logic that expects that peer connection to be present crash

2. The crash seems only to happen when connecting to SIP servers with self-signed certificates, or certificates where not all intermediate certificates are included

[komaxx]

Should I move this issue to the flutter-webrtc repository? It looks like the issue is actually in there?