void UDPPort::OnLocalAddressReady(rtc::AsyncPacketSocket* socket,
                                  const rtc::SocketAddress& address) {
  // When adapter enumeration is disabled and binding to the any address, the
  // default local address will be issued as a candidate instead if
  // |emit_local_for_anyaddress| is true. This is to allow connectivity for
  // applications which absolutely requires a HOST candidate.
  rtc::SocketAddress addr = address;

  // If MaybeSetDefaultLocalAddress fails, we keep the "any" IP so that at
  // least the port is listening.
  MaybeSetDefaultLocalAddress(&addr);

  AddAddress(addr, addr, rtc::SocketAddress(), UDP_PROTOCOL_NAME, "", "",
             LOCAL_PORT_TYPE, ICE_TYPE_PREFERENCE_HOST, 0, "", false);
  MaybePrepareStunCandidate();
}
void UDPPort::MaybePrepareStunCandidate() {
  // Sending binding request to the STUN server if address is available to
  // prepare STUN candidate.
  if (!server_addresses_.empty()) {
    SendStunBindingRequests();
  } else {
    // Port is done allocating candidates.
    MaybeSetPortCompleteOrError();
  }
}

• conclusion
  • 在收集好本地address时，会尝试一次发stun binding request

---

• 会有两处调用OnLocalAddressReady

bool UDPPort::Init() {
  stun_keepalive_lifetime_ = GetStunKeepaliveLifetime();
  if (!SharedSocket()) {
    RTC_DCHECK(socket_ == NULL);
    socket_ = socket_factory()->CreateUdpSocket(
        rtc::SocketAddress(Network()->GetBestIP(), 0), min_port(), max_port());
    if (!socket_) {
      RTC_LOG(LS_WARNING) << ToString() << ": UDP socket creation failed";
      return false;
    }
    socket_->SignalReadPacket.connect(this, &UDPPort::OnReadPacket);
  }
  socket_->SignalSentPacket.connect(this, &UDPPort::OnSentPacket);
  socket_->SignalReadyToSend.connect(this, &UDPPort::OnReadyToSend);
  socket_->SignalAddressReady.connect(this, &UDPPort::OnLocalAddressReady);
  requests_.SignalSendPacket.connect(this, &UDPPort::OnSendPacket);
  return true;
}

• 从代码来看，没有调用SignalAddressReady

void UDPPort::PrepareAddress() {
  RTC_DCHECK(requests_.empty());
  if (socket_->GetState() == rtc::AsyncPacketSocket::STATE_BOUND) {
    OnLocalAddressReady(socket_, socket_->GetLocalAddress());
  }
}

---

void BasicPortAllocatorSession::AddAllocatedPort(Port* port,
                                                 AllocationSequence* seq,
                                                 bool prepare_address) {
  RTC_DCHECK_RUN_ON(network_thread_);
  if (!port)
    return;

  RTC_LOG(LS_INFO) << "Adding allocated port for " << content_name();
  port->set_content_name(content_name());
  port->set_component(component());
  port->set_generation(generation());
  if (allocator_->proxy().type != rtc::PROXY_NONE)
    port->set_proxy(allocator_->user_agent(), allocator_->proxy());
  port->set_send_retransmit_count_attribute(
      (flags() & PORTALLOCATOR_ENABLE_STUN_RETRANSMIT_ATTRIBUTE) != 0);

  PortData data(port, seq);
  ports_.push_back(data);

  port->SignalCandidateReady.connect(
      this, &BasicPortAllocatorSession::OnCandidateReady);
  port->SignalPortComplete.connect(this,
                                   &BasicPortAllocatorSession::OnPortComplete);
  port->SignalDestroyed.connect(this,
                                &BasicPortAllocatorSession::OnPortDestroyed);
  port->SignalPortError.connect(this, &BasicPortAllocatorSession::OnPortError);
  RTC_LOG(LS_INFO) << port->ToString() << ": Added port to allocator";

  if (prepare_address)
    port->PrepareAddress();
}

• conclusion
  • 只能是这里调用PrepareAddress()函数了

---

void AllocationSequence::OnMessage(rtc::Message* msg) {
  RTC_DCHECK(rtc::Thread::Current() == session_->network_thread());
  RTC_DCHECK(msg->message_id == MSG_ALLOCATION_PHASE);

  const char* const PHASE_NAMES[kNumPhases] = {"Udp", "Relay", "Tcp"};

  // Perform all of the phases in the current step.
  RTC_LOG(LS_INFO) << network_->ToString()
                   << ": Allocation Phase=" << PHASE_NAMES[phase_];

  switch (phase_) {
    case PHASE_UDP:
      CreateUDPPorts();
      CreateStunPorts();
      break;
}

• conclusion
  • 这里udp端口和stun端口是串行调用的
  • 但是在CreateStunPorts函数里，由于使用了PORTALLOCATOR_ENABLE_SHARED_SOCKET，直接就返回了。所以说UDPPort类和StunPort类，耦合性很高。
  • 在CreateUDPPorts里会调用session_->AddAllocatedPort(port.release(), this, true);

---

// Performs the allocation of ports, in a sequenced (timed) manner, for a given
// network and IP address.
class AllocationSequence : public rtc::MessageHandler,
                           public sigslot::has_slots<> {
public:
  //这里面会调用下面的几个CreateXXX函数
  // MessageHandler
  void OnMessage(rtc::Message* msg) override;              
private:
  bool IsFlagSet(uint32_t flag) { return ((flags_ & flag) != 0); }
  void CreateUDPPorts();
  void CreateTCPPorts();
  void CreateStunPorts();
  void CreateRelayPorts();
  void CreateGturnPort(const RelayServerConfig& config);

BasicPortAllocatorSession* session_;

};

class RTC_EXPORT PortAllocatorSession : public sigslot::has_slots<> {};
class RTC_EXPORT BasicPortAllocatorSession : public PortAllocatorSession,
                                             public rtc::MessageHandler {};

• conclusion
  • 成员函数session_
  • 这里有两相关的类是导出类

---

• conclusion
  • 通过消息分发，调用到AllocationSequence::OnMessage(rtc::Message)