webrtc ice代码流程走读

1、获取turn、stun服务器信息处理流程
Conductor::InitializePeerConnection

->Conductor::CreatePeerConnection
->PeerConnectionFactory::CreatePeerConnection
->PeerConnection::Initialize
->PeerConnection::InitializePortAllocator_n//这个函数解析配置信息，确定探测类型及参数。

->PortAllocator::SetConfiguration//这里配置服务器信息。

2、生效turn、stun服务器处理流程
WebRtcSessionDescriptionFactory::OnMessage

->Conductor::OnSuccess
->PeerConnection::SetLocalDescription   (session_->MaybeStartGathering())
->WebRtcSession::MaybeStartGathering
->TransportController::MaybeStartGathering
->TransportController::MaybeStartGathering_n
->P2PTransportChannel::MaybeStartGathering
AddAllocatorSession(allocator_->CreateSession());//注册信号量
allocator_sessions_.back()->StartGettingPorts(); //启动Port资源申请消息

当P2PTransportChannel::MaybeStartGathering函数调用BasicPortAllocatorSession::StartGettingPorts后，就会启动MSG_CONFIG_START消息处理流程。开始收集本端的candidates信息。

3、发送candidates信息给对端：
每次调用EnableProtocol函数，就是将本地的Candidates信息，发送给对端的Client
AllocationSequence::EnableProtocol
->BasicPortAllocatorSession::OnProtocolEnabled
->SignalCandidatesReady
->P2PTransportChannel::OnCandidatesReady
->SignalCandidateGathered
->TransportController::OnChannelCandidateGathered_n
->SignalCandidatesGathered
->WebRtcSession::OnTransportControllerCandidatesGathered
->Conductor::OnIceCandidate
->Conductor::SendMessage
->PeerConnectionClient::SendToPeer
Port资源申请结束后，通过信号量传递该信息：
SignalPortAllocationComplete信号量触发调用
BasicPortAllocatorSession::OnPortAllocationComplete

4、接收端

Conductor::OnMessageFromPeer

->PeerConnection::SetRemoteDescription
->WebRtcSession::SetRemoteDescription
->WebRtcSession::UpdateSessionState
->WebRtcSession::PushdownTransportDescription
->WebRtcSession::PushdownRemoteTransportDescription
->TransportController::SetRemoteTransportDescription
->TransportController::SetRemoteTransportDescription_n
->JsepTransport::SetRemoteTransportDescription
->JsepTransport::ApplyRemoteTransportDescription
->P2PTransportChannel::SetRemoteIceParameters

->P2PTransportChannel::RequestSortAndStateUpdate

->P2PTransportChannel::SortConnectionsAndUpdateState

5、心跳检测

webrtc进行ICE探测时，会在不稳定链接时，持续发送ping心跳报文，当检测链接已经稳定后，就不再发心跳报文，也不会探测切换传输路径。

链接是否稳定是在weak函数里面判断的。要是服务器资源宽裕的话，可以把weak修改问false。整个通话期间持续探测。可以做到主备倒换的目的

p2pasep2ptransportchannel.h

6、额外说明

　　webrtc会每隔两秒，检查一下网络状态是否有变化，若是有变化，就重新探测网络，选择其他的传输方式。所以会概率出现一会P2P一会中转的现象。

　　

Network::Network
BasicNetworkManager::CreateNetworks
BasicNetworkManager::UpdateNetworksOnce
BasicNetworkManager::UpdateNetworksContinually
BasicNetworkManager::OnMessage
MessageQueue::Dispatch
Thread::ProcessMessages
Thread::Run
Thread::PreRun

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some from：https://blog.csdn.net/CrystalShaw/article/details/80804225