NSStream TCP保持活躍的iOS

Question

我寫了這個代碼設置一個流與服務器：

-(void)streamOpenWithIp:(NSString *)ip withPortNumber:(int)portNumber; 
{ 
     CFReadStreamRef readStream; 
     CFWriteStreamRef writeStream; 
     CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, (__bridge CFStringRef)ip, portNumber, &readStream, &writeStream); 

     if(readStream && writeStream) 
     { 
      CFReadStreamSetProperty(readStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue); 
      CFWriteStreamSetProperty(writeStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue); 

      //Setup inpustream 
      inputStream = (__bridge NSInputStream *)readStream; 
      [inputStream setDelegate:self]; 
      [inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; 
      [inputStream open]; 

      //Setup outputstream 
      outputStream = (__bridge NSOutputStream *)writeStream; 
      [outputStream setDelegate:self]; 
      [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; 
      [outputStream open]; 
     } 
} 

我能夠連接到服務器併發送&接收數據。但我想檢查連接是否仍然存在。如果我從WiFi路由器斷開連接線，我仍然可以在流中發送數據並且沒有發生錯誤。

您可以通過使用定時器發送一些消息並檢查您是否收到回覆，在應用程序級別解決此問題。但是，您也可以在較低級別上使用TCP Keep-Alive技術來解決此問題。

如何使用NSStream實現這個功能？我怎樣才能設置檢查間隔？

我假設您通過TCP Keep-Alive檢查流時關閉了NSStreamEventErrorOcurred？

我已經檢查了這個職位，但我無法弄清楚： Keeping a socket connection alive in iOS

感謝您的幫助！

Answer 1

這個委託方法給出連接的流狀態。你可以檢查你的連接狀態這裏

-(void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)event { 
    NSLog(@"Stream triggered."); 
    switch(event) { 
      case (NSStreamStatus)NSStreamEventErrorOccurred: 
     { 

      NSLog(@"%@",[stream streamError].localizedDescription); 

     } 
      break; 
     case NSStreamEventHasSpaceAvailable: { 
      if(stream == outputStream) { 
       NSLog(@"outputStream is ready."); 
      } 
      break; 
     } 
     case NSStreamEventHasBytesAvailable: { 
      if(stream == inputStream) { 

        NSLog(@"data can be read here!"); 

       } 
      } 
      break; 
     } 
     default: { 


      NSLog(@"Stream is sending an Event: %i", event); 
      break; 
     } 
    } 
} 

Answer 2

你可以得到本地套接字句柄與

CFDataRef socketData = CFReadStreamCopyProperty((__bridge CFReadStreamRef)(inputStream), kCFStreamPropertySocketNativeHandle); 
CFSocketNativeHandle socket; 
CFDataGetBytes(socketData, CFRangeMake(0, sizeof(CFSocketNativeHandle)), (UInt8 *)&socket); 
CFRelease(socketData); 

，然後設置套接字選項（需要#include <sys/socket.h>此）：

int on = 1; 
if (setsockopt(socket, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1) { 
    NSLog(@"setsockopt failed: %s", strerror(errno)); 
} 

您可以將此代碼放入kCFStreamEventOpenCompleted事件的事件處理函數中：

- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)event { 
    switch (event) { 
     case kCFStreamEventOpenCompleted: 
      if (stream == self.inputStream) { 
       CFDataRef socketData = CFReadStreamCopyProperty((__bridge CFReadStreamRef)(stream), kCFStreamPropertySocketNativeHandle); 
       CFSocketNativeHandle socket; 
       CFDataGetBytes(socketData, CFRangeMake(0, sizeof(CFSocketNativeHandle)), (UInt8 *)&socket); 
       CFRelease(socketData); 

       int on = 1; 
       if (setsockopt(socket, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1) { 
        NSLog(@"setsockopt failed: %s", strerror(errno)); 
       } 
      } 
      break; 

     /* ... other cases ... */; 
    } 
} 

Answer 3

有一個類似問題的更完整的答案。

對於開始10秒後發送保活應用的例子中，發送keppalive每2秒和關閉後4種保活與無應答的流，看看此信息： Is it possible to activate TCP keepalive on Apple iOS devices

它還顯示如何設置連接關閉後的重新傳輸超時。