通过TCP发送0xF8字节

Question

我正在使用Asyncsocket通过TCP发送字节。我有代码工作，但是当发送字节0xF8时，我遇到了问题。

以下是我尝试过的（在下面的评论中）和代码：

NSString *ip_current = self.text_ip.text;
sockethost=ip_current;
socketport=9100;
[self   connect];

//a working one as long as I don't use 0xF8
NSData   *dataStream  = [[NSString stringWithFormat:@"%c%c",0x1d,0x31] dataUsingEncoding:NSUTF8StringEncoding];
[self.socket writeData:dataStream withTimeout:1 tag:1];

 //This one below will give 0x1d, 0xc3,0xb8 (After some research I found that this is due to encoding issue with UTF8)
 NSData   *dataStream  = [[NSString stringWithFormat:@"%c%c", 0x1d, 0xf8 dataUsingEncoding:NSUTF8StringEncoding];
//People suggest that using ASCII encoding, this time I don't get 3 bytes but 2 bytes with wrong data with 1d and 6f(f8 change to 6f)
NSData   *dataStream  = [[NSString stringWithFormat:@"%c%c%c",0x1d,0xf8,0x31] dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];

[self.socket disconnectAfterWriting];

所以，无论我使用什么编码，都有问题。有人知道如何解决这个问题吗？在此先感谢!!!

Answer 1

你只想要一个字节。字符串与此无关。从字节创建NSData，而不是字符串。

uint8_t byte = 0xF8;
NSData *dataStream = [NSData dataWithBytes:&byte length:1];