jrtplib RTP over TCP实现代码剖析

原创

fengyuzaitu 2023-02-16 16:15:26 博主文章分类：视音频 ©著作权

文章标签 jrtplib RTP over TCP 文章分类 C/C++ 后端开发

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前言

GB28181规范指定了RTP over TCP采用的协议格式

简单来说，就是TCP传输RTP/RTCP数据的是时候，先传输报文长度(采用两个字节保存发送)

RFC 4571: Framing Real-time Transport Protocol (RTP) and RTP Control Protocol (RTCP) Packets over Connection-Oriented Transport (rfc-editor.org)

jrtplib RTP over TCP实现代码剖析_jrtplib RTP over TCP

jrtplib RTP over TCP实现代码剖析_jrtplib RTP over TCP_02

代码实现

源码rtptcptransmitter.cpp

发送代码

int RTPTCPTransmitter::SendRTPRTCPData(const void *data, size_t len)
{
  if (!m_init)
    return ERR_RTP_TCPTRANS_NOTINIT;

  MAINMUTEX_LOCK
  
  if (!m_created)
  {
    MAINMUTEX_UNLOCK
    return ERR_RTP_TCPTRANS_NOTCREATED;
  }
  if (len > RTPTCPTRANS_MAXPACKSIZE)
  {
    MAINMUTEX_UNLOCK
    return ERR_RTP_TCPTRANS_SPECIFIEDSIZETOOBIG;
  }
  
  std::map<SocketType, SocketData>::iterator it = m_destSockets.begin();
  std::map<SocketType, SocketData>::iterator end = m_destSockets.end();

  vector<SocketType> errSockets;
  int flags = 0;
#ifdef RTP_HAVE_MSG_NOSIGNAL
  flags = MSG_NOSIGNAL;
#endif // RTP_HAVE_MSG_NOSIGNAL

  while (it != end)
  {
    uint8_t lengthBytes[2] = { (uint8_t)((len >> 8)&0xff), (uint8_t)(len&0xff) };
    SocketType sock = it->first;

    if (send(sock,(const char *)lengthBytes,2,flags) < 0 ||
      send(sock,(const char *)data,len,flags) < 0)
      errSockets.push_back(sock);
    ++it;
  }
  
  MAINMUTEX_UNLOCK

  if (errSockets.size() != 0)
  {
    for (size_t i = 0 ; i < errSockets.size() ; i++)
      OnSendError(errSockets[i]);
  }

  // Don't return an error code to avoid the poll thread exiting
  // due to one closed connection for example

  return 0;
}

接收代码

int RTPTCPTransmitter::SocketData::ProcessAvailableBytes(SocketType sock, int availLen, bool &complete, RTPMemoryManager *pMgr)
{
	JRTPLIB_UNUSED(pMgr); // possibly unused

	const int numLengthBuffer = 2;
	if (m_lengthBufferOffset < numLengthBuffer) // first we need to get the length
	{
		assert(m_pDataBuffer == 0);
		int num = numLengthBuffer-m_lengthBufferOffset;
		if (num > availLen)
			num = availLen;

		int r = 0;
		if (num > 0)
		{
			r = (int)recv(sock, (char *)(m_lengthBuffer+m_lengthBufferOffset), num, 0);
			if (r < 0)
				return ERR_RTP_TCPTRANS_ERRORINRECV;
		}

		m_lengthBufferOffset += r;
		availLen -= r;

		assert(m_lengthBufferOffset <= numLengthBuffer);
		if (m_lengthBufferOffset == numLengthBuffer) // we can constuct a length
		{
			int l = 0;
			for (int i = numLengthBuffer-1, shift = 0 ; i >= 0 ; i--, shift += 8)
				l |= ((int)m_lengthBuffer[i]) << shift;

			m_dataLength = l;
			m_dataBufferOffset = 0;

			//cout << "Expecting " << m_dataLength << " bytes" << endl;

			// avoid allocation of length 0
			if (l == 0)
				l = 1;

			// We don't yet know if it's an RTP or RTCP packet, so we'll stick to RTP
			m_pDataBuffer = RTPNew(pMgr, RTPMEM_TYPE_BUFFER_RECEIVEDRTPPACKET) uint8_t[l];
			if (m_pDataBuffer == 0)
				return ERR_RTP_OUTOFMEM;
		}
	}

	if (m_lengthBufferOffset == numLengthBuffer && m_pDataBuffer) // the last one is to make sure we didn't run out of memory
	{
		if (m_dataBufferOffset < m_dataLength)
		{
			int num = m_dataLength-m_dataBufferOffset;
			if (num > availLen)
				num = availLen;

			int r = 0;
			if (num > 0)
			{
				r = (int)recv(sock, (char *)(m_pDataBuffer+m_dataBufferOffset), num, 0);
				if (r < 0)
					return ERR_RTP_TCPTRANS_ERRORINRECV;
			}

			m_dataBufferOffset += r;
			availLen -= r;
		}

		if (m_dataBufferOffset == m_dataLength)
			complete = true;
	}
	return 0;
}