iphone - 如何在后台保持VOIP套接字连接？

Question

我的应用程序要求:由于某些原因，我应该保持套接字连接以触发服务器推送上的本地通知，而不使用推送通知 (APN)。所以我使用iPhone的VOIP后台功能来维持套接字连接。

<强>1。我已经为 VOIP 配置了一个流，以便保持套接字连接在后台运行，那么我应该设置什么超时值？一旦超时，socket连接会终止吗？如何让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];

<强>2。我应该在处理程序 applicationDidEnterBackground 中重新连接流吗:

   [[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];

    }];

<强>3。假设我的服务器重新启动并且应用程序处于后台，我如何确保连接？ 如果我的 iPhone 中的 Wi-Fi 连接或者我终止了服务器应用程序，则连接将被关闭，那么我应该采取什么措施来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。一旦套接字中有可用数据，您的应用程序就会收到 CPU 时间。所以在 runLoop 中我正在检查 ht

在我的例子中，信号协议(protocol)在一个单独的线程中工作，所以我自己旋转 runLoop

  // 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，我在将它们调度到 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;
  }

当您的套接字为您提供一些信息时，即使您的应用程序在后台，这些函数也会被调用:

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
  }
}

为了让服务器知道客户端仍然处于事件状态，我们每 10 分钟向服务器发送一次 ping 命令，因此 KeepAlive 处理程序设置为 600。您可以使用其他值来节省电池，但这会使断开连接的检测变得更糟在客户端和服务器端。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;
}];

这是为了确保在发送 ping 并等待服务器对 ping 的回复之前应用程序不会被挂起。此外，如果套接字已经断开连接，则可能需要重新连接，这将需要一些时间并且需要进程在后台运行。

但请确保在不再需要后台任务时正确释放它们。否则，当超过 bg 超时时，应用程序将被系统杀死。