NSStream TCP Keep-alive iOS

我已经写了这个代码来设置一个服务器的stream：

-(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]; } } 

我可以连接到服务器并发送和接收数据。 但是我想检查连接是否仍然存在。 如果我从无线路由器断开连接线，我仍然可以发送stream中的数据，没有发生错误。

你可以通过使用计时器来发送一些消息并检查是否收到回复，从而在应用程序级别上解决这个问题。 但是，您也可以在较低级别上使用TCP Keep-Alive技术来解决此问题。

我如何用NSStream实现这个？ 我怎样才能设置检查间隔？

我假设你通过TCP Keep-Alive来检查stream时是否收到NSStreamEventErrorOcurred？

我已经检查了这个post，但我无法弄清楚： 在iOS中保持套接字连接

谢谢你的帮助！

Answer 1

你可以得到原生的套接字句柄

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

然后设置套接字选项（你需要#include <sys/socket.h> ）：

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

你可以把这段代码放在kCFStreamEventOpenCompleted事件的事件处理函数中：

 - (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 2

这个委托方法给出连接的stream状态。 你可以在这里检查你的连接状态

  -(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 3

有一个类似的问题更完整的答案。

对于10秒后开始发送Keepalive的应用程序示例，每隔2秒发送一次keppalive，并在4个keepalive之后closuresstream，不回复，看看这篇文章： 是否可以在Apple iOS设备上激活TCP keepalive

它还显示了如何设置连接closures后的重新传输超时。