Null result on Converting NSData to NSString - objective-c

Question

I am facing a problem when converting NSData to NSString. I'm using UTF8Enconding but the result is null!!
Here is the data I receive <100226ab c0a8010b 00000000 00000000> it must be either 192.168.1.11 or 192.168.1.17.
This is the method I use to convert :
NSString *ipAddress = [[NSString alloc] initWithData:address encoding:NSUTF8StringEncoding];
Is there anything wrong?!
By the way, This the did receive data delegate of GCDAsyncUdpSocket library.

Answer 1

From the documentation of GCDAsyncUdpSocket:
The localAddress method returns a sockaddr structure wrapped in a
NSData object.
The following code unwraps the data to a sockaddr structure and converts the IP address to a NSString. It works with IPv4 and IPv6 addresses.
#include <sys/socket.h>
#include <netdb.h>
NSData *data = ...; // your data
NSLog(#"data = %#", data);
// Copy data to a "sockaddr_storage" structure.
struct sockaddr_storage sa;
socklen_t salen = sizeof(sa);
[data getBytes:&sa length:salen];
// Get host from socket address as C string:
char host[NI_MAXHOST];
getnameinfo((struct sockaddr *)&sa, salen, host, sizeof(host), NULL, 0, NI_NUMERICHOST);
// Convert C string to NSString:
NSString *ipAddress = [[NSString alloc] initWithBytes:host length:strlen(host) encoding:NSUTF8StringEncoding];
NSLog(#"strAddr = %#", ipAddress);
Output:
data = <100226ab c0a8010b 00000000 00000000>
strAddr = 192.168.1.11

Answer 2

This is not a string response. This is binary data. If you consider <100226ab c0a8010b 00000000 00000000>, look at the coa8010b: c0 in hex is equal to 192 in decimal, a8 = 168, 01 = 1, and 0b = 11. In short, this is a binary representation, not a string representation, of 192.168.1.11.
You may want to more carefully examine the GCDAsyncUdpSocket documentation for the nature of response you should get, as it's apparently binary data, not a string.

Answer 3

I guess there is problem with the encoding . I have also faced similar issue and solved by:
NSString *responseString =[[NSString alloc] initWithBytes:[data bytes] length:[data length] encoding:NSUnicodeStringEncoding];

Answer 4

Found a much quicker way to do it, using inet_ntoa():
//Get the bytes from the data and cast it to the correct struct
struct sockaddr_in *addr = (struct sockaddr_in *)[address bytes];
//inet_ntoa converts from the binary format to a C string
NSString *IP = [NSString stringWithCString:inet_ntoa(addr->sin_addr) encoding:NSASCIIStringEncoding];

Answer 5

First try with other encoding formats available
1. NSASCIIStringEncoding
2. NSMacOSRomanStringEncoding
3. NSShiftJISStringEncoding.
even if it not works,try like the following ways
1. NSData *data = [NSData dataWithContentsOfURL:URL];
// Assuming data is in UTF8.
NSString *string = [NSString stringWithUTF8String:[data bytes]];
2. This is like as you done.
// if data is in another encoding, for example ISO-8859-1
NSString *string = [[NSString alloc]
initWithData:data encoding: NSISOLatin1StringEncoding];