1、獲取turn、stun服務器信息處理流程
Conductor::InitializePeerConnection
->Conductor::CreatePeerConnection
->PeerConnectionFactory::CreatePeerConnection
->PeerConnection::Initialize
->PeerConnection::InitializePortAllocator_n//這個函數解析配置信息，確定探測類型及參數。
->PortAllocator::SetConfiguration//這裏配置服務器信息。
2、生效turn、stun服務器處理流程
WebRtcSessionDescriptionFactory::OnMessage
->Conductor::OnSuccess
->PeerConnection::SetLocalDescription (session_->MaybeStartGathering())
->WebRtcSession::MaybeStartGathering
->TransportController::MaybeStartGathering
->TransportController::MaybeStartGathering_n
->P2PTransportChannel::MaybeStartGathering
AddAllocatorSession(allocator_->CreateSession());//註冊信號量
allocator_sessions_.back()->StartGettingPorts(); //啓動Port資源申請消息
當P2PTransportChannel::MaybeStartGathering函數調用BasicPortAllocatorSession::StartGettingPorts後，就會啓動MSG_CONFIG_START消息處理流程。開始收集本端的candidates信息。
3、發送candidates信息給對端：
每次調用EnableProtocol函數，就是將本地的Candidates信息，發送給對端的Client
AllocationSequence::EnableProtocol
->BasicPortAllocatorSession::OnProtocolEnabled
->SignalCandidatesReady
->P2PTransportChannel::OnCandidatesReady
->SignalCandidateGathered
->TransportController::OnChannelCandidateGathered_n
->SignalCandidatesGathered
->WebRtcSession::OnTransportControllerCandidatesGathered
->Conductor::OnIceCandidate
->Conductor::SendMessage
->PeerConnectionClient::SendToPeer
Port資源申請結束後，通過信號量傳遞該信息：
SignalPortAllocationComplete信號量觸發調用
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、心跳檢測
webrtc進行ICE探測時，會在不穩定鏈接時，持續發送ping心跳報文，當檢測鏈接已經穩定後，就不再發心跳報文，也不會探測切換傳輸路徑。
鏈接是否穩定是在weak函數裏面判斷的。要是服務器資源寬裕的話，可以把weak修改問false。整個通話期間持續探測。可以做到主備倒換的目的
p2p\base\p2ptransportchannel.h
6、額外說明
webrtc會每隔兩秒，檢查一下網絡狀態是否有變化，若是有變化，就重新探測網絡，選擇其他的傳輸方式。所以會概率出現一會P2P一會中轉的現象。
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