Darwin Streaming Server中RTSP会话流程解析(Darwin流媒体服务器解析1)

一、首先是本地监听的建立：StartServer() ->

                                                  -->QTSServer::Initialize()

                                                            --->QTSServer::CreateListeners() //函数中根据本地xml配置文件中的rtsp_port进行监听的建立                                   

                                                   -->QTSServer::StartTasks() //开启Socket读取

具体函数在:

QTSServer::CreateListeners()
{
…
              newListenerArray[curPortIndex] = NEW RTSPListenerSocket();
            QTSS_Error err = newListenerArray[curPortIndex]->Initialize(thePortTrackers[count3].fIPAddr, thePortTrackers[count3].fPort);//fIPAddr为本地IP,fPort为配置端口号

…
}

void QTSServer::StartTasks()
{
    fRTCPTask = new RTCPTask();
    fStatsTask = new RTPStatsUpdaterTask();

    //
    // Start listening
    for (UInt32 x = 0; x < fNumListeners; x++)
        fListeners[x]->RequestEvent(EV_RE);
}

二、会话建立

先看RTSPListenerSocket类：

Socket的读取统一归于EventContext类中的EventThread线程，具体到EventThread::Entry()中的select_waitevent()捕获。

EventThread::Entry()函数中查找EventThread::fRefTable，获取对应的EventContext。得到的是EventContext类型的派生类RTSPListenerSocket。

EventThread::Entry()
{

…
     EventContext* theContext = (EventContext*)ref->GetObject();
     theContext->ProcessEvent(theCurrentEvent.er_eventbits);
…

}

调用RTSPListenerSocket的ProcessEvent()函数，进而调用TCPListenerSocket::ProcessEvent()，在TCPListenerSocket::ProcessEvent()中accept Socket

	
    theTask = this->GetSessionTask(&theSocket);//创建RTSPSession
    if (theTask == NULL)
    {    //this should be a disconnect. do an ioctl call?
        close(osSocket);
        if (theSocket)
            theSocket->fState &= ~kConnected; // turn off connected state
    }
    else
    {   
        Assert(osSocket != EventContext::kInvalidFileDesc);
        
        //set options on the socket
        //we are a server, always disable nagle algorithm
        int one = 1;
        int err = ::setsockopt(osSocket, IPPROTO_TCP, TCP_NODELAY, (char*)&one, sizeof(int));
        AssertV(err == 0, OSThread::GetErrno());
        
        err = ::setsockopt(osSocket, SOL_SOCKET, SO_KEEPALIVE, (char*)&one, sizeof(int));
        AssertV(err == 0, OSThread::GetErrno());
    
        int sndBufSize = 96L * 1024L;
        err = ::setsockopt(osSocket, SOL_SOCKET, SO_SNDBUF, (char*)&sndBufSize, sizeof(int));
        AssertV(err == 0, OSThread::GetErrno());
    
        //setup the socket. When there is data on the socket,
        //theTask will get an kReadEvent event
        theSocket->Set(osSocket, &addr);
        theSocket->InitNonBlocking(osSocket);
        theSocket->SetTask(theTask);      //将处理Socket的类转入到RTSPSession
        theSocket->RequestEvent(EV_RE);   //将当前Socket加入select侦听队列
    }
  

将(TCPSocket*)theSocket加入到侦听队列中，从上以后就开始对该条已建立accept的(TCPSocket*)theSocket描述请求由此处所创建的(RTSPSession*)theTask进行处理。

三、RTSP交互

        同样Socket的读取统一归于EventContext类中的EventThread线程，具体到EventThread::Entry()中的select_waitevent()捕获。

EventThread::Entry()函数中查找EventThread::fRefTable，获取对应的EventContext。此时查找到第二部分中加入到侦听队列的Socket，进入

到EventContext中的ProcessEvent()函数：

virtual void ProcessEvent(int /*eventBits*/) 
        {   
            if (EVENTCONTEXT_DEBUG)
            {
                if (fTask== NULL)  
                    qtss_printf("EventContext::ProcessEvent context=%lu task=NULL\n",(UInt32) this); 
                else 
                    qtss_printf("EventContext::ProcessEvent context=%lu task=%lu TaskName=%s\n",(UInt32)this,(UInt32) fTask, fTask->fTaskName); 
            }

            if (fTask != NULL)
                fTask->Signal(Task::kReadEvent); 
        }

激活第二部分中theSocket所映射的theTask，进行Socket读取。此处fTask就是RTSPSession类。把RTSPSession加入到TaskThread的队列等待RTSPSession::Run()被调用，

进而就是RTSPSession::Run()对具体的RTSP请求进行的处理。

好了，今天就简单推进到此处，下一部分将深入到RTSPSession中具体对报文如何解析，以及RTSPSession如何与其他模块&Task进行交互进行分析！

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