live555已经发展了十几年了，不得不钦佩作者坚持不懈的奉献和国外的开源生态环境，live555可以说是大部分的安防从业者的入门之选，尤其是在嵌入式或者Linux系统上，其应用还是蛮广泛的，主要是其兼容性和稳定性；

但是随着live555十几年的不断迭代，很多开发者反复向作者Ross提到的多线程和IPv6的功能，作者也一直都没有去尝试，可能是这样会对live555的架构产生比较大的改动和影响，作者为了稳妥，选择了小改动、稳定、逐步迭代的方式, 虽然是性能稳定，但支持的路数有限，不能多线程工作始终是个坎; 网上找到几篇live555多线程的博客, 基本上大同小异，就是创建独立的UsageEnvironment和TaskSchedule, 由独立的线程分工协作; 本人也是这个思路,创建多个工作线程,每个工作线程内创建UsageEnvironment和TaskSchedule,然后各自开启EventLoop;

今天我们抛砖引玉，先大概聊一下主体思路，在后续的博客中将尽力完整地汇总这些思路和开发的过程：

目标

将live555修改为多线程, 每个通道对应一个工作线程,由工作线程对该通道进行独立处理;

大体修改点

修改支持多线程, 主要涉及到以下类的修改

• GenericMediaServer
• RTSPServer

GenericMediaServer.cpp
在GenericMediaServer的构造函数中, 创建工作线程个数,即最大支持的通道数;

GenericMediaServer

::GenericMediaServer(UsageEnvironment& env, int ourSocketV4, int ourSocketV6, Port ourPort,

             unsigned reclamationSeconds)

  : Medium(env),

    fServerSocket4(ourSocketV4), fServerSocket6(ourSocketV6),

    fServerPort(ourPort), fReclamationSeconds(reclamationSeconds),

    fServerMediaSessions(HashTable::create(STRING_HASH_KEYS)),

    fClientConnections(HashTable::create(ONE_WORD_HASH_KEYS)),

    fClientSessions(HashTable::create(STRING_HASH_KEYS)) {

  ignoreSigPipeOnSocket(fServerSocket4); // so that clients on the same host that are killed don't also kill us

  ignoreSigPipeOnSocket(fServerSocket6); // so that clients on the same host that are killed don't also kill us

#ifdef LIVE_MULTI_THREAD_ENABLE

  InitMutex(&mutexClientConnection);

  memset(&multiThreadCore, 0x00, sizeof(MultiThread_CORE_T));

  multiThreadCore.threadNum = MAX_DEFAULT_MULTI_THREAD_NUM;

  multiThreadCore.threadTask = new LIVE_THREAD_TASK_T[multiThreadCore.threadNum];

  memset(&multiThreadCore.threadTask[0], 0x00, sizeof(LIVE_THREAD_TASK_T) * multiThreadCore.threadNum);

  for (int i=0; i<multiThreadCore.threadNum; i++)

  {

      char szName[36] = {0};

      sprintf(szName, "worker thread %d", i);

      multiThreadCore.threadTask[i].id = i;

      multiThreadCore.threadTask[i].extPtr = this;

      multiThreadCore.threadTask[i].pSubScheduler = BasicTaskScheduler::createNew();

      multiThreadCore.threadTask[i].pSubEnv = BasicUsageEnvironment::createNew(*multiThreadCore.threadTask[i].pSubScheduler, i+1, szName);

      CreateOSThread( &multiThreadCore.threadTask[i].osThread, __OSThread_Proc, (void *)&multiThreadCore.threadTask[i] );

  }

#endif

  // Arrange to handle connections from others:

  env.taskScheduler().turnOnBackgroundReadHandling(fServerSocket4, incomingConnectionHandler4, this);

  env.taskScheduler().turnOnBackgroundReadHandling(fServerSocket6, incomingConnectionHandler6, this);

}

接受客户端连接

按原有流程接受客户端连接;

分配客户端请求

在收到客户端发送的DESCRIBE命令后,
在通道列表中找出空闲的通道，将该客户端关联到该通道, 然后从主线程中移除该socket, 由工作线程接管该socket的操作;
后续有客户端如访问已经存在的通道,则主线程会将该请求直接分配给对应的工作线程处理;

注意: 主线程的工作到此结束，不要执行lookupServerMediaSession的操作;

在工作线程中, 接管客户端的socket后, 马上执行lookupServerMediaSession, 在该函数中，将后缀回调给上层调用程序, 由上层调用程序判断是否存在该通道，如不存在则返回失败，如存在则向前端取流，然后填充媒体信息返回成功, 库内部则创建相应的mediasession, 再回应客户端, 后续的则完成整个rtsp流程的交互;

注意: 创建MediaSession时，必须将工作线程中的UsageEnvironment传进去, 不能使用主线程中的envir();

int RTSPServer::RTSPClientConnection

::handleCmd_DESCRIBE(UsageEnvironment *pEnv, char const* urlPreSuffix, char const* urlSuffix, char const* fullRequestStr, LIVE_THREAD_TASK_T **pThreadTask)

{

    int handleCmdRet = 0;

  ServerMediaSession* session = NULL;

  char* sdpDescription = NULL;

  char* rtspURL = NULL;

  do {

    char urlTotalSuffix[2*RTSP_PARAM_STRING_MAX];

        // enough space for urlPreSuffix/urlSuffix'\0'

    urlTotalSuffix[0] = '\0';

    if (urlPreSuffix[0] != '\0') {

      strcat(urlTotalSuffix, urlPreSuffix);

      strcat(urlTotalSuffix, "/");

    }

    strcat(urlTotalSuffix, urlSuffix);

    if (!authenticationOK("DESCRIBE", urlTotalSuffix, fullRequestStr)) break;

    // We should really check that the request contains an "Accept:" #####

    // for "application/sdp", because that's what we're sending back #####

    _TRACE(TRACE_LOG_DEBUG, "handleCmd_DESCRIBE  socket[%d]\n", this->fOurSocket);

    #ifdef LIVE_MULTI_THREAD_ENABLE

    //如果当前是主线程,则进入到查找通道流程

    if (pEnv->GetEnvirId() == 1000)

    {

        fOurServer.LockClientConnection();  //Lock

        UsageEnvironment  *pChEnv = fOurServer.GetEnvBySuffix(urlSuffix, this, pThreadTask);

        if (NULL == pChEnv)

        {

            fOurServer.UnlockClientConnection();        //Unlock

            handleCmdRet = -1;

            this->assignSink = False;

            this->pEnv = NULL;

            handleCmd_notFound();

            break;

        }

        else

        {

            _TRACE(TRACE_LOG_DEBUG, "将socket[%d] 关联到[%s]\n", this->fOurSocket, pChEnv->GetEnvirName());

            //将socket从主线程移到工作线程中

            UsageEnvironment  *pMainEnv = &envir();

            envir().taskScheduler().disableBackgroundHandling(fOurSocket);

            fOurServer.UnlockClientConnection();        //Unlock

            return 1000;

        }

        break;

    }

    #endif

    // Begin by looking up the "ServerMediaSession" object for the specified "urlTotalSuffix":

    //在工作线程中执行 lookupServerMediaSession

    session = fOurServer.lookupServerMediaSession(pEnv, 1, this, urlTotalSuffix);

    if (session == NULL) {

        //pChEnv->taskScheduler().disableBackgroundHandling(fOurSocket);

        _TRACE(TRACE_LOG_DEBUG, "socket[%d] 在[%s]中, 源未就绪[%s]\n", this->fOurSocket, pEnv->GetEnvirName(), urlTotalSuffix);

        this->assignSink = False;

        this->pEnv = NULL;

        handleCmdRet = -1;

        //envir().taskScheduler().disableBackgroundHandling(fOurSocket);

        //fOurServer.ResetEnvBySuffix(urlSuffix, this);

        handleCmd_notFound();

        break;

    }

    session->incrementReferenceCount();

    // Then, assemble a SDP description for this session:

    sdpDescription = session->generateSDPDescription(fOurIPVer);

    if (sdpDescription == NULL) {

      // This usually means that a file name that was specified for a

      // "ServerMediaSubsession" does not exist.

      setRTSPResponse("404 File Not Found, Or In Incorrect Format");

      break;

    }

    unsigned sdpDescriptionSize = strlen(sdpDescription);

    // Also, generate our RTSP URL, for the "Content-Base:" header

    // (which is necessary to ensure that the correct URL gets used in subsequent "SETUP" requests).

    rtspURL = fOurRTSPServer.rtspURL(session, fOurIPVer, fClientInputSocket);

    snprintf((char*)fResponseBuffer, sizeof fResponseBuffer,

         "RTSP/1.0 200 OK\r\nCSeq: %s\r\n"

         "%s"

         "Content-Base: %s/\r\n"

         "Content-Type: application/sdp\r\n"

         "Content-Length: %d\r\n\r\n"

         "%s",

         fCurrentCSeq,

         dateHeader(),

         rtspURL,

         sdpDescriptionSize,

         sdpDescription);

  } while (0);

  if (session != NULL) {

    // Decrement its reference count, now that we're done using it:

    session->decrementReferenceCount();

    if (session->referenceCount() == 0 && session->deleteWhenUnreferenced()) {

      fOurServer.removeServerMediaSession(pEnv, session, True);

    }

    session->SetStreamStatus(1);        //置标志,让后续访问该通道的客户端可以得到迅速响应

  }

  delete[] sdpDescription;

  delete[] rtspURL;

  return handleCmdRet;

}

历经2个多月，终于将多线程问题搞定. 在此记录一下, 欢迎探讨;

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