H:\webrtc-20210315\webrtc-20210315\webrtc\webrtc-checkout\src\p2p\client\basic_port_allocator.cc
AllocationSequence的作用就是用于分配UDPPort和RelayPort，里面创建了Candidate。

AllocationSequence类

AllocationSequence创建时机

BasicPortAllocatorSession::DoAllocate

AllocationSequence::Init

CreateUdpSocket

H:\webrtc-20210315\webrtc-20210315\webrtc\webrtc-checkout\src\p2p\base\basic_packet_socket_factory.cc
AsyncPacketSocket* CreateUdpSocket(const SocketAddress& local_address, uint16_t min_port, uint16_t max_port) override;

CreateAsyncSocket

AsyncSocket* PhysicalSocketServer::CreateAsyncSocket(int family, int type)

SocketDispatcher::Create

PhysicalSocket::Create

SocketDispatcher::Initialize

bool SocketDispatcher::Initialize() {
  RTC_DCHECK(s_ != INVALID_SOCKET);
// Must be a non-blocking
#if defined(WEBRTC_WIN)
  u_long argp = 1;
  ioctlsocket(s_, FIONBIO, &argp);
#elif defined(WEBRTC_POSIX)
  fcntl(s_, F_SETFL, fcntl(s_, F_GETFL, 0) | O_NONBLOCK);
#endif
#if defined(WEBRTC_IOS)
  // iOS may kill sockets when the app is moved to the background
  // (specifically, if the app doesn't use the "voip" UIBackgroundMode). When
  // we attempt to write to such a socket, SIGPIPE will be raised, which by
  // default will terminate the process, which we don't want. By specifying
  // this socket option, SIGPIPE will be disabled for the socket.
  int value = 1;
  ::setsockopt(s_, SOL_SOCKET, SO_NOSIGPIPE, &value, sizeof(value));
#endif
  ss_->Add(this);
  return true;
}

创建Socket的调用栈

小结

1、收集candidate
2、BasicPortAllocatorSession::DoAllocate
3、看创建socket的调用堆栈