如何在后台维护VOIP套接字连接？

Question

我的应用程序要求:出于某些原因,我应该维护套接字连接以在服务器推送时触发本地通知,而不使用推送通知(APN).所以我使用iPhone的VOIP后台功能来维护套接字连接.

1.我为VOIP配置了一个流,以便继续在后台运行套接字连接,那么我应该设置什么超时值？一旦超时到期,套接字连接是否会终止？如何使我的应用程序始终监听套接字.

客户端流配置如下,

NSString *urlStr = @"http://192.168.0.108";
NSURL *website = [NSURL URLWithString:urlStr];
CFReadStreamRef readStream;
CFWriteStreamRef writeStream;
CFStreamCreatePairWithSocketToHost(NULL, (CFStringRef)[website host], 1234, &readStream, &writeStream);

CFReadStreamSetProperty(readStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);
CFWriteStreamSetProperty(writeStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);    

NSInputStream *inputStream = (NSInputStream *)readStream;
NSOutputStream *outputStream = (NSOutputStream *)writeStream;
[inputStream setDelegate:self];
[inputStream setProperty:NSStreamNetworkServiceTypeVoIP forKey:NSStreamNetworkServiceType] ;
[outputStream setDelegate:self];
[outputStream setProperty:NSStreamNetworkServiceTypeVoIP forKey:NSStreamNetworkServiceType] ;
[inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[inputStream open];
[outputStream open];

2.我应该在处理程序applicationDidEnterBackground中重新连接流:

   [[UIApplication sharedApplication] setKeepAliveTimeout:86400 handler:^(void) 
{

    if (inputStream)
        [inputStream close];
    if (outputStream)
        [outputStream close];


    urlStr = @"http://192.168.0.108";
    website = [NSURL URLWithString:urlStr];
    CFStreamCreatePairWithSocketToHost(NULL, (CFStringRef)[website host], 1234, &readStream, &writeStream);
    CFReadStreamSetProperty(readStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);
    CFWriteStreamSetProperty(writeStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);    
    inputStream = (NSInputStream *)readStream;
    outputStream = (NSOutputStream *)writeStream;
    [inputStream setDelegate:self];
    [inputStream setProperty:NSStreamNetworkServiceTypeVoIP forKey:NSStreamNetworkServiceType] ;
    [outputStream setDelegate:self];
    [outputStream setProperty:NSStreamNetworkServiceTypeVoIP forKey:NSStreamNetworkServiceType] ;
    [inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [inputStream open];
    [outputStream open];

    }];

3.说我的服务器重新启动,应用程序在后台,我该如何确保连接？ 如果我的iPhone中的Wi-Fi连接或我终止服务器应用程序将关闭连接,那么我应该采取什么措施使我的应用程序按预期工作？

Answer 1

您还需要确保已在pList文件中设置

<key>UIBackgroundModes</key>
<array>
    <string>voip</string>
</array>

当您的应用程序在后台时,套接字将由iOS管理.只要插槽中有数据,您的应用程序就会收到CPU时间.所以在runLoop我正在检查ht

在我的情况下,信令协议在一个单独的线程中工作,所以我正在旋转runLoop我自己

  // Start runloop
  while (!m_needStop) 
  {
    CFRunLoopRun();
  }

并在需要时停止它:

  m_needStop = true;
  {
    QAutoLock l(m_runLoopGuard);
    if ( m_runLoop != NULL )
      CFRunLoopStop(m_runLoop);
  }

对于runLoop中的套接字,我在将它们安排到runLoop之前设置了处理函数:

  int nFlags = kCFStreamEventOpenCompleted | kCFStreamEventHasBytesAvailable | kCFStreamEventCanAcceptBytes | kCFStreamEventErrorOccurred | kCFStreamEventEndEncountered;
  CFStreamClientContext context;
  context.info = this;
  context.version = 0;
  context.release = NULL;
  context.retain = NULL;
  context.copyDescription = NULL;

  if ( !CFReadStreamSetClient(m_readStream, nFlags, NotificationProtocolHandler::ReadStreamCallback, &context) )
  {
    ReleaseStreams();
    return false;
  }

  if ( !CFWriteStreamSetClient(m_writeStream, nFlags, NotificationProtocolHandler::WriteStreamCallback, &context) )
  {
    ReleaseStreams();
    return false;
  }

这些函数将在您的套接字为您提供一些信息时调用,即使您的应用程序在后台运行:

void NotificationProtocolHandler::ReadStreamCallback(CFReadStreamRef stream,
                                                     CFStreamEventType eventType,
                                                     void *clientCallBackInfo)
{      
  NotificationProtocolHandler* handler = (NotificationProtocolHandler*)clientCallBackInfo;
  switch (eventType)
  {
    case kCFStreamEventOpenCompleted:
      break;

    case kCFStreamEventHasBytesAvailable:
      handler->ProcessInput();
      break;

    case kCFStreamEventErrorOccurred:
      handler->ProcessConnectionError();
      break;

    case kCFStreamEventEndEncountered:
      handler->ProcessConnectionError();
      break;

    default:
      break; // do nothing
  }
}

void NotificationProtocolHandler::WriteStreamCallback(CFWriteStreamRef stream,
                                                      CFStreamEventType eventType,
                                                      void *clientCallBackInfo)
{
  NotificationProtocolHandler* handler = (NotificationProtocolHandler*)clientCallBackInfo;

  switch (eventType)
  {
    case kCFStreamEventOpenCompleted:
      handler->ProcessOutputConnect();
      break;

    case kCFStreamEventCanAcceptBytes:
      handler->ProcessReadyToWrite();
      break;

    case kCFStreamEventErrorOccurred:
      handler->ProcessConnectionError();
      break;

    case kCFStreamEventEndEncountered:
      handler->ProcessConnectionError();
      break;     

    default:
      break; // do nothing
  }
}

为了使服务器知道客户端仍处于活动状态,我们每隔10分钟将ping命令发送到服务器,因此KeepAlive处理程序设置为600.您可以使用其他值来节省电池,但会检测到客户端上的断开连接会更糟糕和服务器端.并且会增加断开连接和重新连接之间的时间.

BOOL scheduled = [app setKeepAliveTimeout:pingTimeout handler:^{ // Schedule processing after some time interval      

  SchedulePing(0);
}

SchedulePing(0)将执行如下:

StartLongBGTask();
if ( avoidFinishBgTask != NULL )
  *avoidFinishBgTask = true;
m_pingTimer = CreateTimer(pingTimeout, PingTimerCallback); // result is ignored

而StartLongBGTask是一个

m_bgTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler: ^{
  [[UIApplication sharedApplication] endBackgroundTask:m_bgTask];
  m_bgTask = UIBackgroundTaskInvalid;
}];

这需要确保在发送ping并等待来自服务器的ping回复之前不会挂起应用程序.此外,如果套接字已经断开连接,则可能需要重新连接,这将花费一些时间并且需要proccess在后台运行.

但是,当您不再需要它们时,请务必正确释放后台任务.当超过bg超时时,系统将杀死其他明智的应用程序.