TCP客户端无法以永久循环方式进行通信

Question

我想让TCP客户端在永久循环中发送和接收数据。我尝试过以下代码，但数据发送和接收只执行一次。

理想：

iOS ------> server
iOS <------ server
iOS ------> server
iOS <------ server
  and forever ...

问题：

iOS ------> server
iOS <------ server
  one time only

我的服务器代码没有问题，因为我已经在客户端本机c代码中测试了它。所以，我想知道我的Swift代码是否有问题。

var sendFlag:Bool = true;
func initTcpNetwork(host:String,port :Int,delegate:NSStreamDelegate? ) {

    NSStream.getStreamsToHostWithName(host, port: port, inputStream: &inputstream, outputStream: &outputstream)

    inputstream?.delegate=self;
    outputstream?.delegate=self;


    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0)){
        self.printQueueLabel();
        let loop = NSRunLoop.currentRunLoop();
        self.inputstream?.scheduleInRunLoop(loop, forMode: NSDefaultRunLoopMode);
        self.outputstream?.scheduleInRunLoop(loop, forMode: NSDefaultRunLoopMode);
        self.inputstream?.open()
        self.outputstream?.open()
        loop.run();

    }

}

func stream(aStream: NSStream, handleEvent eventCode: NSStreamEvent) {
    switch (eventCode){
    case NSStreamEvent.OpenCompleted:
        NSLog("Stream opened");
        break
    case NSStreamEvent.HasSpaceAvailable:
        NSLog("has space");
        if(sendFlag) {
            sendFlag = false;
            var outputstream = aStream as? NSOutputStream;
            var str = "0";

            var data: NSData = str.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!;
            outputstream?.write(UnsafePointer<UInt8>(data.bytes), maxLength: data.length);
        }

        break
    case NSStreamEvent.HasBytesAvailable:
        var inputstream = aStream as? NSInputStream;

        var buffer = [UInt8](count: 4096, repeatedValue: 0);
        while ((inputstream?.hasBytesAvailable) != nil) {
            var len = inputstream?.read(&buffer, maxLength: 4096);
            if (len > 0) {
                var output: NSString = NSString(bytes:&buffer, length:len!, encoding:NSASCIIStringEncoding)!;
                dispatch_async(dispatch_get_main_queue(), {
                    self.handleDataReceived(output);
                })
            }
        }
        self.sendFlag = true;

        break
    case NSStreamEvent.ErrorOccurred:
        var err = aStream.streamError;
        print(err?.description);

        break
    case NSStreamEvent.EndEncountered:
        aStream.close();
        aStream.removeFromRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode);
        break
    default:
        NSLog("unknown.")
    }
}