Crtmp 源码分析

Crtmp Server接收rtmp音视频流，并实现音视频并发，可以作为直播后台的服务。整套代码量并不大，算是轻量级的服务。

花了些时间研究源码，现将研究的结果，记录下来，方便以后查阅。

先不从架构上分析，直接看代码。我是将crtmp运行在windows环境下，所以代码分析以windows参考。

//这个方法在一个while循环里执行
bool IOHandlerManager::Pulse() {
    if (_isShuttingDown)
        return false;
    //1. Create a copy of all fd sets
    FD_ZERO(&_readFdsCopy);
    FD_ZERO(&_writeFdsCopy);
    FD_ZERO(&_writeFdsCopy);
    FD_COPY(&_readFds, &_readFdsCopy);
    FD_COPY(&_writeFds, &_writeFdsCopy);

    //2. compute the max fd
    if (_activeIOHandlers.size() == )
        return true;

    //3. do the select
　　//检查读写fd集合是否有变化。
    RESET_TIMER(_timeout, , );
    int32_t count = select(MAP_KEY(--_fdState.end()) + , &_readFdsCopy, &_writeFdsCopy, NULL, &_timeout);
    if (count < ) {
        FATAL("Unable to do select: %u", (uint32_t) LASTSOCKETERROR);
        return false;
    }

    _pTimersManager->TimeElapsed(time(NULL));

    if (count == ) {
        return true;
    }

    //4. Start crunching the sets
    // _activeIOHandlers 是以IOHandler为父类的类集合。这些类在构造函数里将自己
　　//添加到_activeIOHandlers 中。没有外来连接请求来时 _activeIOHandlers
   //已经存在IOHandler子类，要不下面的内容永远执行不到。
　　//这些IOHandler子类时在configure moudle创建的
    FOR_MAP(_activeIOHandlers, uint32_t, IOHandler *, i) {
        if (FD_ISSET(MAP_VAL(i)->GetInboundFd(), &_readFdsCopy)) {
            _currentEvent.type = SET_READ;
            if (!MAP_VAL(i)->OnEvent(_currentEvent))
                EnqueueForDelete(MAP_VAL(i));
        }
        if (FD_ISSET(MAP_VAL(i)->GetOutboundFd(), &_writeFdsCopy)) {
            _currentEvent.type = SET_WRITE;
            if (!MAP_VAL(i)->OnEvent(_currentEvent))
                EnqueueForDelete(MAP_VAL(i));
        }
    }

    return true;
}

　　configure module

bool Module::BindAcceptors() {
//accpetors 来自lua脚本。如下图1所示，脚本中有3个acceptor。
    FOR_MAP(config[CONF_ACCEPTORS], string, Variant, i) {
        if (!BindAcceptor(MAP_VAL(i))) {
            FATAL("Unable to configure acceptor:\n%s", STR(MAP_VAL(i).ToString()));
            return false;
        }
    }
    return true;
}

bool Module::BindAcceptor(Variant &node) {
    //1. Get the chain
    vector<uint64_t> chain;
　　// CONF_PROTOCOL 表示 "protocol"，ResolveProtocolChain代码在下面，该方法
   //执行后的返回值chain 包含的内容是PT_TCP,PT_INBOUND_RTMP.
    chain = ProtocolFactoryManager::ResolveProtocolChain(node[CONF_PROTOCOL]);
    if (chain.size() == ) {
        WARN("Invalid protocol chain: %s", STR(node[CONF_PROTOCOL]));
        return true;
    }

    //2. Is it TCP or UDP based?
    if (chain[] == PT_TCP) {
        //3. This is a tcp acceptor. Instantiate it and start accepting connections
　　　　　//创建TCP Acceptor,以图1第一组数据来看，ip为0.0.0.0，port 为1935，node为图1第一组数据
        //chain包含的内容有PT_TCP,PT_INBOUND_RTM。
        TCPAcceptor *pAcceptor = new TCPAcceptor(node[CONF_IP],
                node[CONF_PORT], node, chain);
　　　　　　　//调用Bind方法，具体方法内容在下面
        if (!pAcceptor->Bind()) {
            FATAL("Unable to fire up acceptor from this config node: %s",
                    STR(node.ToString()));
            return false;
        }
        ADD_VECTOR_END(acceptors, pAcceptor);
        return true;
    } else if (chain[] == PT_UDP) {
        //4. Ok, this is an UDP acceptor. Because of that, we can instantiate
        //the full stack. Get the stack first
        BaseProtocol *pProtocol = ProtocolFactoryManager::CreateProtocolChain(
                chain, node);
        if (pProtocol == NULL) {
            FATAL("Unable to instantiate protocol stack %s", STR(node[CONF_PROTOCOL]));
            return false;
        }

        //5. Create the carrier and bind it
        UDPCarrier *pUDPCarrier = UDPCarrier::Create(node[CONF_IP], node[CONF_PORT],
                pProtocol);
        if (pUDPCarrier == NULL) {
            FATAL("Unable to instantiate UDP carrier on %s:%hu",
                    STR(node[CONF_IP]), (uint16_t) node[CONF_PORT]);
            pProtocol->EnqueueForDelete();
            return false;
        }
        pUDPCarrier->SetParameters(node);
        ADD_VECTOR_END(acceptors, pUDPCarrier);

        //6. We are done
        return true;
    } else {
        FATAL("Invalid carrier type");
        return false;
    }
}

vector<uint64_t> DefaultProtocolFactory::ResolveProtocolChain(string name) {
 vector<uint64_t> result;
 if (false) {

}
#ifdef HAS_PROTOCOL_DNS
 else if (name == CONF_PROTOCOL_INBOUND_DNS) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_DNS);
 } else if (name == CONF_PROTOCOL_OUTBOUND_DNS) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_OUTBOUND_DNS);
 }
#endif /* HAS_PROTOCOL_DNS */
#ifdef HAS_PROTOCOL_RTMP
 else if (name == CONF_PROTOCOL_INBOUND_RTMP) {

//图1的第一组数据对应添加的协议类型在这里
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_RTMP);
 } else if (name == CONF_PROTOCOL_OUTBOUND_RTMP) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_OUTBOUND_RTMP);
 } else if (name == CONF_PROTOCOL_INBOUND_RTMPS) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_SSL);
  ADD_VECTOR_END(result, PT_INBOUND_RTMPS_DISC);
 }
#ifdef HAS_PROTOCOL_HTTP
 else if (name == CONF_PROTOCOL_INBOUND_RTMPT) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_HTTP);
  ADD_VECTOR_END(result, PT_INBOUND_HTTP_FOR_RTMP);
 }
#endif /* HAS_PROTOCOL_HTTP */
#endif /* HAS_PROTOCOL_RTMP */
#ifdef HAS_PROTOCOL_TS
 else if (name == CONF_PROTOCOL_INBOUND_TCP_TS) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_TS);
 } else if (name == CONF_PROTOCOL_INBOUND_UDP_TS) {
  ADD_VECTOR_END(result, PT_UDP);
  ADD_VECTOR_END(result, PT_INBOUND_TS);
 }
#endif /* HAS_PROTOCOL_TS */
#ifdef HAS_PROTOCOL_RTP
 else if (name == CONF_PROTOCOL_INBOUND_RTSP) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_RTSP);
 } else if (name == CONF_PROTOCOL_RTSP_RTCP) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_RTSP);
  ADD_VECTOR_END(result, PT_RTCP);
 } else if (name == CONF_PROTOCOL_UDP_RTCP) {
  ADD_VECTOR_END(result, PT_UDP);
  ADD_VECTOR_END(result, PT_RTCP);
 } else if (name == CONF_PROTOCOL_INBOUND_RTSP_RTP) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_RTSP);
  ADD_VECTOR_END(result, PT_INBOUND_RTP);
 } else if (name == CONF_PROTOCOL_INBOUND_UDP_RTP) {
  ADD_VECTOR_END(result, PT_UDP);
  ADD_VECTOR_END(result, PT_INBOUND_RTP);
 } else if (name == CONF_PROTOCOL_RTP_NAT_TRAVERSAL) {
  ADD_VECTOR_END(result, PT_UDP);
  ADD_VECTOR_END(result, PT_RTP_NAT_TRAVERSAL);
 }
#endif /* HAS_PROTOCOL_RTP */
#ifdef HAS_PROTOCOL_HTTP
 else if (name == CONF_PROTOCOL_OUTBOUND_HTTP) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_OUTBOUND_HTTP);
 }
#endif /* HAS_PROTOCOL_HTTP */
#ifdef HAS_PROTOCOL_LIVEFLV
 else if (name == CONF_PROTOCOL_INBOUND_LIVE_FLV) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_LIVE_FLV);
 }
#endif /* HAS_PROTOCOL_LIVEFLV */
#ifdef HAS_PROTOCOL_VAR
 else if (name == CONF_PROTOCOL_INBOUND_XML_VARIANT) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_XML_VAR);
 } else if (name == CONF_PROTOCOL_INBOUND_BIN_VARIANT) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_BIN_VAR);
 } else if (name == CONF_PROTOCOL_OUTBOUND_XML_VARIANT) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_XML_VAR);
 } else if (name == CONF_PROTOCOL_OUTBOUND_BIN_VARIANT) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_BIN_VAR);
 }
#ifdef HAS_PROTOCOL_HTTP
 else if (name == CONF_PROTOCOL_INBOUND_HTTP_XML_VARIANT) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_HTTP);
  ADD_VECTOR_END(result, PT_XML_VAR);
 } else if (name == CONF_PROTOCOL_INBOUND_HTTP_BIN_VARIANT) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_HTTP);
  ADD_VECTOR_END(result, PT_BIN_VAR);
 } else if (name == CONF_PROTOCOL_OUTBOUND_HTTP_XML_VARIANT) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_OUTBOUND_HTTP);
  ADD_VECTOR_END(result, PT_XML_VAR);
 } else if (name == CONF_PROTOCOL_OUTBOUND_HTTP_BIN_VARIANT) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_OUTBOUND_HTTP);
  ADD_VECTOR_END(result, PT_BIN_VAR);
 }
#endif /* HAS_PROTOCOL_HTTP */
#endif /* HAS_PROTOCOL_VAR */
#ifdef HAS_PROTOCOL_CLI
 else if (name == CONF_PROTOCOL_INBOUND_CLI_JSON) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_JSONCLI);
 }
#ifdef HAS_PROTOCOL_HTTP
 else if (name == CONF_PROTOCOL_INBOUND_HTTP_CLI_JSON) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_HTTP);
  ADD_VECTOR_END(result, PT_HTTP_4_CLI);
  ADD_VECTOR_END(result, PT_INBOUND_JSONCLI);
 }
#endif /* HAS_PROTOCOL_HTTP */
#endif /* HAS_PROTOCOL_CLI */
#ifdef HAS_PROTOCOL_MMS
 else if (name == CONF_PROTOCOL_OUTBOUND_MMS) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_OUTBOUND_MMS);
 }
#endif /* HAS_PROTOCOL_MMS */
#ifdef HAS_PROTOCOL_RAWHTTPSTREAM
 else if (name == CONF_PROTOCOL_INBOUND_RAW_HTTP_STREAM) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_RAW_HTTP_STREAM);
 } else if (name == CONF_PROTOCOL_INBOUND_RAW_HTTPS_STREAM) {
  ADD_VECTOR_END(result, PT_TCP);
  ADD_VECTOR_END(result, PT_INBOUND_SSL);
  ADD_VECTOR_END(result, PT_INBOUND_RAW_HTTP_STREAM);
 }
#endif /* HAS_PROTOCOL_RAWHTTPSTREAM */
 else {
  FATAL("Invalid protocol chain: %s.", STR(name));
 }
 return result;
}

bool TCPAcceptor::Bind() {

//创建socket
 _inboundFd = _outboundFd = (int) socket(PF_INET, SOCK_STREAM, 0);
 if (_inboundFd < 0) {
  int err = LASTSOCKETERROR;
  FATAL("Unable to create socket: %s(%d)", strerror(err), err);
  return false;
 }

if (!setFdOptions(_inboundFd)) {
  FATAL("Unable to set socket options");
  return false;
 }

//将创建socket绑定到ip 为0.0.0.0，port为1935的socket address中。

if (bind(_inboundFd, (sockaddr *) & _address, sizeof (sockaddr)) != 0) {
  int error = LASTSOCKETERROR;
  FATAL("Unable to bind on address: tcp://%s:%hu; Error was: %s (%d)",
    inet_ntoa(((sockaddr_in *) & _address)->sin_addr),
    ENTOHS(((sockaddr_in *) & _address)->sin_port),
    strerror(error),
    error);
  return false;
 }

if (_port == 0) {
  socklen_t tempSize = sizeof (sockaddr);
  if (getsockname(_inboundFd, (sockaddr *) & _address, &tempSize) != 0) {
   FATAL("Unable to extract the random port");
   return false;
  }
  _parameters[CONF_PORT] = (uint16_t) ENTOHS(_address.sin_port);
 }

//监听新创建的socket fd，什么时候执行Accept是通过select模型来实现的，但需要将fd添加到select监控

//的fd集合中，这是在activate acceptor中完成的。具体代码在见下面。

if (listen(_inboundFd, 100) != 0) {
  FATAL("Unable to put the socket in listening mode");
  return false;
 }

_enabled = true;
 return true;
}

bool BaseClientApplication::ActivateAcceptor(IOHandler *pIOHandler) {
 switch (pIOHandler->GetType()) {
  case IOHT_ACCEPTOR:
  {
   TCPAcceptor *pAcceptor = (TCPAcceptor *) pIOHandler;
   pAcceptor->SetApplication(this);
   return pAcceptor->StartAccept();
  }
  case IOHT_UDP_CARRIER:
  {
   UDPCarrier *pUDPCarrier = (UDPCarrier *) pIOHandler;
   pUDPCarrier->GetProtocol()->GetNearEndpoint()->SetApplication(this);
   return pUDPCarrier->StartAccept();
  }
  default:
  {
   FATAL("Invalid acceptor type");
   return false;
  }
 }
}

bool TCPAcceptor::StartAccept() {

//该方法将TCPAcceptor创建的fd添加到全局的fd集合中

//当有连接请求进来时，端口号1935上来了连接请求，主循环中select方法会返回，

//在fd集合中根据相应的fd找到它归属的TCPAcceptor，并调用TCPAcceptor的ONEvent方法
 return IOHandlerManager::EnableAcceptConnections(this);
}

bool TCPAcceptor::OnEvent(select_event &event) {
 if (!OnConnectionAvailable(event))
  return IsAlive();
 else
  return true;
}

bool TCPAcceptor::OnConnectionAvailable(select_event &event) {
 if (_pApplication == NULL)
  return Accept();
 return _pApplication->AcceptTCPConnection(this);
}

bool TCPAcceptor::Accept() {
 sockaddr address;
 memset(&address, 0, sizeof (sockaddr));
 socklen_t len = sizeof (sockaddr);
 int32_t fd;
 int32_t error;

//1. Accept the connection

//OnEvent方法会调用这个间接调用改方法
 fd = accept(_inboundFd, &address, &len);
 error = LASTSOCKETERROR;
 if (fd < 0) {
  FATAL("Unable to accept client connection: %s (%d)", strerror(error), error);
  return false;
 }
 if (!_enabled) {
  CLOSE_SOCKET(fd);
  _droppedCount++;
  WARN("Acceptor is not enabled. Client dropped: %s:%hu -> %s:%hu",
    inet_ntoa(((sockaddr_in *) & address)->sin_addr),
    ENTOHS(((sockaddr_in *) & address)->sin_port),
    STR(_ipAddress),
    _port);
  return true;
 }
 INFO("Client connected: %s:%hu -> %s:%hu",
   inet_ntoa(((sockaddr_in *) & address)->sin_addr),
   ENTOHS(((sockaddr_in *) & address)->sin_port),
   STR(_ipAddress),
   _port);

if (!setFdOptions(fd)) {
  FATAL("Unable to set socket options");
  CLOSE_SOCKET(fd);
  return false;
 }

//4. Create the chain

//创建协议，以图1中第一组数据为例，_protocolChain中包含PT_TCP,PT_INBOUND_RTMP

//这里共创建两个协议，tcp Protocol和 inbound rtmp,且tcp协议的near Protocol指向

//inbound rtmp 返回 inbound rtmp协议
 BaseProtocol *pProtocol = ProtocolFactoryManager::CreateProtocolChain(
   _protocolChain, _parameters);
 if (pProtocol == NULL) {
  FATAL("Unable to create protocol chain");
  CLOSE_SOCKET(fd);
  return false;
 }

//5. Create the carrier and bind it
 TCPCarrier *pTCPCarrier = new TCPCarrier(fd);

//pProtocol->GetFarEndpoint()指向tcp protocol。
 pTCPCarrier->SetProtocol(pProtocol->GetFarEndpoint());
 pProtocol->GetFarEndpoint()->SetIOHandler(pTCPCarrier);

//6. Register the protocol stack with an application
 if (_pApplication != NULL) {
  pProtocol = pProtocol->GetNearEndpoint();
  pProtocol->SetApplication(_pApplication);
 }

//调用tcp protocol 相应的方法

if (pProtocol->GetNearEndpoint()->GetOutputBuffer() != NULL)
  pProtocol->GetNearEndpoint()->EnqueueForOutbound();

_acceptedCount++;

//7. Done
 return true;
}

Variant & TCPAcceptor::GetParameters() {
 return _parameters;
}

　　　　　　　　　　 图1 acceptors

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