如何从 Web 服务获取流类型的数据

我想用相应的URL从服务器读取流数据，目前我正在尝试使用NSInputStream读取数据，但是我收到错误"错误2操作无法完成。没有这样的文件或目录"。Web开发人员以字节格式接收数据，然后将该数据转换为Stream，如MemoryStream(byteData([注意：Web服务是用.net编写的]，并将相同的内容返回给我。读取这种数据的方法是什么，我尝试了AISHTTPRequest得到了大小为0字节的文件，我再次尝试了NSURLConnction，我得到了大小为0字节的文件，现在我正在使用NSInputStream，我得到了开头提到的错误。这是我的NSInputStream代码，

请指导我是否可以读取这种数据是iOS作为前端，如果是然后指导我应该如何与此类数据交互的方式。如果NSInputStream是与之交互的预期方式，那么下面编写的代码中的问题是什么。

- (void)setUpStreamForFile {
    NSString *urlStr = @"http://192.168.1.201/example/example.svc/example?parameter={'"DCU_DocId'":'"05e24018-b728-4ec8-9848-d6cae02bec95'"}";
    // iStream is NSInputStream instance variable
    iStream = [[NSInputStream alloc] initWithFileAtPath:urlStr];
    [iStream setProperty:[NSDictionary dictionaryWithObjectsAndKeys:(id) kCFBooleanFalse,    kCFStreamSSLValidatesCertificateChain, nil ] forKey:(NSString *) kCFStreamPropertySSLSettings];
    [iStream setDelegate:self];
    [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
                       forMode:NSDefaultRunLoopMode];
    [iStream open];
}
- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)eventCode {
    _data = [[NSMutableData alloc] init];
    int bytesRead=0;
    switch(eventCode) {
        case NSStreamEventHasBytesAvailable:
        {
            if(!_data) {
            }
            uint8_t buf[20480];
            unsigned int len = 0;
            len = [(NSInputStream *)stream read:buf maxLength:20480];
            if(len) {
                [_data appendBytes:(const void *)buf length:len];
                // bytesRead is an instance variable of type NSNumber.
                //[bytesRead setIntValue:[bytesRead intValue]+len];
                bytesRead = bytesRead +len;
                NSLog(@"bytesRead:%d",bytesRead);
            }
            else {
                NSLog(@"no buffer!");
            }
            break;
        }
        case NSStreamEventEndEncountered:
        {
            [stream close];
            [stream removeFromRunLoop:[NSRunLoop currentRunLoop]
                              forMode:NSDefaultRunLoopMode];
            stream = nil; // stream is ivar, so reinit it
            break;
        }
        case NSStreamEventErrorOccurred:
        {
            NSError *theError = [stream streamError];
            UIAlertView *theAlert = [[UIAlertView alloc] initWithTitle:@"" message:[NSString stringWithFormat:@"Error %i: %@",[theError code], [theError localizedDescription]] delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
            NSLog(@"Error %i %@",[theError code], [theError localizedDescription]);
            [theAlert show];
            [stream close];
            break;
        }
        case NSStreamEventOpenCompleted:
        {
            NSLog(@"EventOpen");
        }
        case NSStreamEventHasSpaceAvailable:
        {
             NSLog(@"EventHasSpac");
        }
        case NSStreamEventNone:
        {
            NSLog(@"EventNone");
        }
       }
}