Question

如何计算目标C中的广播地址

我希望将广播地址解析为与以下子网计算器中显示的结果相同的结果 - http://www.subnet-calculator.com/subnet.php

我有本地IOS设备的IP地址和子网掩码。我知道广播地址使用以下公式

broadcast = ip | ( ~ subnet )

（我正在回答我的问题，因为我在互联网上没有看到过这个，而且我也不知道有任何图书馆执行这个计算。很高兴看到是否有其他人有更好的解决方案或知道任何库）

Answer 1

替代解决方案：

#include <net/ethernet.h>
#include <arpa/inet.h>

NSString *localIPAddress = @"192.168.1.10";
NSString *netmaskAddress = @"255.255.192.0";

// Strings to in_addr:
struct in_addr localAddr;
struct in_addr netmaskAddr;
inet_aton([localIPAddress UTF8String], &localAddr);
inet_aton([netmaskAddress UTF8String], &netmaskAddr);

// The broadcast address calculation:
localAddr.s_addr |= ~(netmaskAddr.s_addr);

// in_addr to string:
NSString *broadCastAddress = [NSString stringWithUTF8String:inet_ntoa(localAddr)];

Answer 2

您无需提供IP地址＆amp; subnet-mask用于计算任何网络接口的“广播”地址。实际上你不需要手动计算它。

有ifaddrs Structure描述网络主机。它提供了任何网络接口的完整详细信息。通过使用getifaddrs()方法，您可以检索网络的广播地址，而无需提供IP＆amp;子网掩码作为属性。函数本身检索细节。我更喜欢这个，因为这会使代码更通用。

我在我的代码中使用它。

#import <ifaddrs.h> // for interface addresses needed to find local IP

static NSString * broadcastAddress()
//Gets Local IP of the device over Wifi
//Calculates & returns broadcast Address for the network
{
    NSString * broadcastAddr= @"Error";
    struct ifaddrs *interfaces = NULL;
    struct ifaddrs *temp_addr = NULL;
    int success = 0;

    // retrieve the current interfaces - returns 0 on success
    success = getifaddrs(&interfaces);

    if (success == 0)
    {
        temp_addr = interfaces;

        while(temp_addr != NULL)
        {
            // check if interface is en0 which is the wifi connection on the iPhone
            if(temp_addr->ifa_addr->sa_family == AF_INET)
            {
                if([[NSString stringWithUTF8String:temp_addr->ifa_name] isEqualToString:@"en0"])
                {
                    broadcastAddr = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_dstaddr)->sin_addr)];

                }
            }

            temp_addr = temp_addr->ifa_next;
        }
    }

    freeifaddrs(interfaces);
    return broadcastAddr;
}

详细了解ifaddrs structure See this

Answer 3

以下代码可用于计算广播地址，您只需要NSString类型中的IP地址和子网掩码来执行计算。

////////////////////////////////////////////////////////
// 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);

在Objective-C中计算广播地址

3 个答案: