Question

我做了连接到tcp流服务器的简单应用程序（汽车中的OBD wifi连接）。它连接并且运行良好 - 我可以发送消息并从汽车获得答案。现在我想从回答中只读取指定的数据。当我向汽车发送请求时，例如01041，它会回答这样的事情：

搜索：好的

41 04 7F

我想创建一个只包含此答案的最后一个字节的变量。在这个例子中它将是7F。我想这样做因为我想在Label中提供这些数据。所以我需要在这个示例行中跳过搜索并跳过第2行中的前2个字节以仅获得7F。我怎么能这样做？

   @implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}
- (void)initNetworkCommunication {
    CFReadStreamRef readStream;
    CFWriteStreamRef writeStream;
    CFStreamCreatePairWithSocketToHost(NULL, (CFStringRef)@"192.168.0.10", 35000, &readStream, &writeStream);
    self.inputStream = objc_unretainedObject(readStream);
    self.outputStream = objc_unretainedObject(writeStream);
    [self.inputStream setDelegate:self];
    [self.outputStream setDelegate:self];
    [self.inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

    [self.inputStream open];
    [self.outputStream open];
}
- (IBAction)Connect:(id)sender {
    [self initNetworkCommunication];
}

- (IBAction)Play:(id)sender {
    NSString *response  = [NSString stringWithFormat:@"01041\r\n"];
    [NSThread sleepForTimeInterval:0.05];
    NSData *data = [[NSData alloc] initWithData:[response dataUsingEncoding:NSUTF8StringEncoding]];

}
-(void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
    switch (eventCode) {

        case NSStreamEventOpenCompleted:
            [self.logTextView setText:[self.logTextView.text stringByAppendingString:@"Stream opened\n"]];
            break;

        case NSStreamEventHasBytesAvailable:

            if (aStream == self.inputStream) {

                uint8_t buffer[1024];
                long len;

                while ([self.inputStream hasBytesAvailable]) {
                    len = [self.inputStream read:buffer maxLength:sizeof(buffer)];
                    if (len > 0) {


                        NSString *output = [[NSString alloc] initWithBytes:buffer length:len encoding:NSASCIIStringEncoding];
                        //NSString *oborty = [[NSString alloc] initWithBytes:buffer length:len encoding:NSASCIIStringEncoding];

                        if (nil != output) {
                            [self.logTextView setText:[self.logTextView.text stringByAppendingString:output]];
                            [self.RPM setText:[self.RPM.text stringByAppendingString:output]];
                        }
                    }
                }
            }
            break;

        case NSStreamEventErrorOccurred:
            [self.logTextView setText:[self.logTextView.text stringByAppendingString:@"Can not connect to the host!"]];
            break;

        case NSStreamEventEndEncountered:
            break;

        default:
            NSLog(@"Unknown event");
    }

}

- (IBAction)sendCode:(id)sender {

    NSString *command = self.commandTextField.text;

    NSString *response  = [NSString stringWithFormat:@"%@\r\n", command];

    NSData *data = [[NSData alloc] initWithData:[response dataUsingEncoding:NSUTF8StringEncoding]];
    [self.outputStream write:[data bytes] maxLength:[data length]];
}
@end

我在http://www.raywenderlich.com教程的帮助下完成了tcp连接，所以我不太了解解决我的问题。

这一行[self.RPM setText：[self.RPM.text stringByAppendingString：output]];在Label中显示答案，但它显示了一切。我想我需要创建新的变量输出并以某种方式编辑它，但我不知道如何

如何从流中获取特定数据？

0 个答案: