live555 groupsock

live555 groupsock

groupsock的繼承關係

在OnDemandServerMediaSubsession 類中創建一個Groupsock，Groupsock的繼承關係如上圖所示。Groupsock()構造函數中的做了三件事情

• socket()構造函數建立UDP socket
• 創建destRecord結構記錄
• 創建GroupEId

Groupsock* OnDemandServerMediaSubsession
::createGroupsock(struct in_addr const& addr, Port port) {
  // Default implementation; may be redefined by subclasses:
  return new Groupsock(envir(), addr, port, 255);
}

Groupsock::Groupsock(UsageEnvironment& env, struct in_addr const& groupAddr,
		     Port port, u_int8_t ttl)
  : OutputSocket(env, port),
    deleteIfNoMembers(False), isSlave(False),
    fDests(new destRecord(groupAddr, port, ttl, 0, NULL)),
    fIncomingGroupEId(groupAddr, port.num(), ttl) {
	//如果地址是組播地址則加入多播組
  if (!socketJoinGroup(env, socketNum(), groupAddr.s_addr)) {
    if (DebugLevel >= 1) {
      env << *this << ": failed to join group: "
	  << env.getResultMsg() << "\n";
    }
  }

  // Make sure we can get our source address: 測試是否可以獲得IP地址
  if (ourIPAddress(env) == 0) {
    if (DebugLevel >= 0) { // this is a fatal error
      env << "Unable to determine our source address: "
	  << env.getResultMsg() << "\n";
    }
  }

  if (DebugLevel >= 2) env << *this << ": created\n";
}

OutputSocket()構造函數如下

OutputSocket::OutputSocket(UsageEnvironment& env, Port port)
  : Socket(env, port),
    fSourcePort(0), fLastSentTTL(256/*hack: a deliberately invalid value*/) {
}

Socket::Socket(UsageEnvironment& env, Port port)
  : fEnv(DefaultUsageEnvironment != NULL ? *DefaultUsageEnvironment : env), fPort(port) {
  fSocketNum = setupDatagramSocket(fEnv, port);
}

int setupDatagramSocket(UsageEnvironment& env, Port port) {
  if (!initializeWinsockIfNecessary()) {
    socketErr(env, "Failed to initialize 'winsock': ");
    return -1;
  }

  int newSocket = createSocket(SOCK_DGRAM);
  if (newSocket < 0) {
    socketErr(env, "unable to create datagram socket: ");
    return newSocket;
  }

  int reuseFlag = groupsockPriv(env)->reuseFlag;
  reclaimGroupsockPriv(env);
  if (setsockopt(newSocket, SOL_SOCKET, SO_REUSEADDR,
		 (const char*)&reuseFlag, sizeof reuseFlag) < 0) {
    socketErr(env, "setsockopt(SO_REUSEADDR) error: ");
    closeSocket(newSocket);
    return -1;
  }

#if defined(__WIN32__) || defined(_WIN32)
  // Windoze doesn't properly handle SO_REUSEPORT or IP_MULTICAST_LOOP
#else
#ifdef SO_REUSEPORT
  if (setsockopt(newSocket, SOL_SOCKET, SO_REUSEPORT,
		 (const char*)&reuseFlag, sizeof reuseFlag) < 0) {
    socketErr(env, "setsockopt(SO_REUSEPORT) error: ");
    closeSocket(newSocket);
    return -1;
  }
#endif

#ifdef IP_MULTICAST_LOOP
  const u_int8_t loop = 1;
  if (setsockopt(newSocket, IPPROTO_IP, IP_MULTICAST_LOOP,
		 (const char*)&loop, sizeof loop) < 0) {
    socketErr(env, "setsockopt(IP_MULTICAST_LOOP) error: ");
    closeSocket(newSocket);
    return -1;
  }
#endif
#endif

  // Note: Windoze requires binding, even if the port number is 0
  netAddressBits addr = INADDR_ANY;
#if defined(__WIN32__) || defined(_WIN32)
#else
  if (port.num() != 0 || ReceivingInterfaceAddr != INADDR_ANY) {
#endif
    if (port.num() == 0) addr = ReceivingInterfaceAddr;
    MAKE_SOCKADDR_IN(name, addr, port.num());
    if (bind(newSocket, (struct sockaddr*)&name, sizeof name) != 0) {
      char tmpBuffer[100];
      sprintf(tmpBuffer, "bind() error (port number: %d): ",
	      ntohs(port.num()));
      socketErr(env, tmpBuffer);
      closeSocket(newSocket);
      return -1;
    }
#if defined(__WIN32__) || defined(_WIN32)
#else
  }
#endif

  // Set the sending interface for multicasts, if it's not the default:
  if (SendingInterfaceAddr != INADDR_ANY) {
    struct in_addr addr;
    addr.s_addr = SendingInterfaceAddr;

    if (setsockopt(newSocket, IPPROTO_IP, IP_MULTICAST_IF,
		   (const char*)&addr, sizeof addr) < 0) {
      socketErr(env, "error setting outgoing multicast interface: ");
      closeSocket(newSocket);
      return -1;
    }
  }

  return newSocket;
}