0x02, 0x03 Hex-chars In Objective-c - String - Stack Overflow

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Learn more about Labs 0x02, 0x03 hex-chars in objective-c Ask Question Asked 12 years, 4 months ago Modified 12 years, 4 months ago Viewed 4k times 0

I'm currently working on a server-client project and i'm writing a little tcp iPhone app client. The problem is, that I've to send the server a "packet" with the following formae:

0x02 + a string + 0x09 + an int + 0x03

The problem is, that I don't know how to include the 0x02 (as hex). At the end, I should send everything as NSData.

Here is what I've got so far.

unsigned char tag_start = 0x02; unsigned char tag_end = 0x03; unsigned char tag_split = 0x09; NSString * stringToSend = [NSString stringWithFormat: @"%c%@%c%@%c%@%c%@%c", tag_start, oobject, tag_split, oid, tag_split, oaction, tag_split, ovalue, tag_end]; NSData * dataToSend = [[NSData alloc] initWithData:[stringToSend dataUsingEncoding:NSASCIIStringEncoding]];

• objective-c
• string
• char
• hex

Share Improve this question Follow edited Jul 16, 2012 at 14:26 Cajunluke 3,1132929 silver badges2828 bronze badges asked Jul 16, 2012 at 13:20 LukasLukas 1,35677 gold badges2424 silver badges5050 bronze badges 3

• Wrong is, that the, STX 0x02 will change to NSString 0x32 – Thomas Commented Jul 16, 2012 at 14:15
• To convert an NSInteger (or an unsigned char) to a hex string, you can use the %x format specifier for NSString. Something like this: [NSString stringWithFormat@"0x%x", tag_start"] would produce 0x2 (which is the same value as 0x02). – Andrew Riebe Commented Jul 16, 2012 at 14:20
• Thank's for this tipp, but it doesn't work. The chars in the result aren't STX, ETX, CSM. – Lukas Commented Jul 19, 2012 at 6:34

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3 Answers 3

Sorted by: Reset to default Highest score (default) Trending (recent votes count more) Date modified (newest first) Date created (oldest first) 0

try this way:

NSString *_command = @"\x02...\x09...\x03";

it should be working.

Share Improve this answer Follow answered Jul 16, 2012 at 14:40 holexholex 24k77 gold badges6363 silver badges7777 bronze badges Add a comment | 0

I used, in a similar problem, the NSMutableData and worked then with appendBytes (to append STX, ETX, CSM) or appendData (NSString).

Share Improve this answer Follow answered Jul 16, 2012 at 14:18 ThomasThomas 33011 silver badge1111 bronze badges 1

• Thanks for the reply. I've tried this already, but got problems to add the STX,... How have you managed to add them? – Lukas Commented Jul 17, 2012 at 10:48

Add a comment | 0

Heres how it works:

NSMutableData * mutableData = [[NSMutableData alloc] init]; // Appends STX [mutableData appendData: [NSData dataWithBytes: "\x02" length:1]]; // Appends ETX [mutableData appendData: [NSData dataWithBytes: "\x09" length:1]]; // Appends CSM [mutableData appendData: [NSData dataWithBytes: "\x03" length:1]];

My problem was that the server didn't respond to my messages, but the messages were correct.

Share Improve this answer Follow answered Jul 29, 2012 at 17:27 LukasLukas 1,35677 gold badges2424 silver badges5050 bronze badges Add a comment |

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