Calculating the Broadcast Address in Objective-C

Question

How do I go about calculating the Broadcast Address in Objective C

I would like to have the Broadcast Address resolve to the same result as shown in the following Su

Answer 1

The following code can be used to calculate the broadcast address, all you need is the IP Address and the Subnet Mask in a NSString type to perform the calculation.

////////////////////////////////////////////////////////
// Calculates the local broadcast packet from Local IP Address and Subnet Mask.
// Uses the following calculation:-
// broadcast = ip | ( ~ subnet )   i.e. Broadcast = ip-addr OR the inverted subnet-mask
////////////////////////////////////////////////////////

// Local IP Address and Subnet Mask
NSString *localIPAddress = @"192.168.1.10";
NSString *netmaskAddress = @"255.255.192.0";

// Separate out the subnet mask values and assign them to variables as integers
NSScanner* scannerNetmask = [NSScanner scannerWithString:netmaskAddress];
[scannerNetmask setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:@"."]];
int aNetmask, bNetmask, cNetmask, dNetmask;
[scannerNetmask scanInt:&aNetmask];
[scannerNetmask scanInt:&bNetmask];
[scannerNetmask scanInt:&cNetmask];
[scannerNetmask scanInt:&dNetmask];

// Separate out the ip address values and assign them to variables as integers
NSScanner* scannerLocalIP = [NSScanner scannerWithString:localIPAddress];
[scannerLocalIP setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:@"."]];
int aLocalIP, bLocalIP, cLocalIP, dLocalIP;
[scannerLocalIP scanInt:&aLocalIP];
[scannerLocalIP scanInt:&bLocalIP];
[scannerLocalIP scanInt:&cLocalIP];
[scannerLocalIP scanInt:&dLocalIP];

// Calculate the bitwise inversion of the Netmask
// Do this by first casting value as a unsigned char (1 byte, no complement)
unsigned char biNetmask, ciNetmask, diNetmask;
biNetmask = ~(unsigned char)bNetmask;
ciNetmask = ~(unsigned char)cNetmask;
diNetmask = ~(unsigned char)dNetmask;

// Calculating the separated values for the broadcast address
unsigned char bBroadcast, cBroadcast, dBroadcast;
bBroadcast = (unsigned char)bLocalIP | biNetmask;
cBroadcast = (unsigned char)cLocalIP | ciNetmask;
dBroadcast = (unsigned char)dLocalIP | diNetmask;

// Create the Broadcast Address from separate values and display in the console
NSString broadcastAddress = [NSString stringWithFormat:@"%d.%d.%d.%d", aLocalIP, bBroadcast, cBroadcast, dBroadcast];
 NSLog(@"Broadcast Address: %@", broadcastAddress);