1. A,B,C IP Address
(1) Public A,B,C IP Address
A: 0.0.0.0 ~ 127.255.255.255
B: 128.0.0.0 ~ 191.255.255.255
C: 192.0.0.0 ~ 223.255.255.255
(2) Private internal A,B,C IP Address
A: 10.0.0.0 ~ 10.255.255.255
B: 172.16.0.0 ~ 172.31.255.255
C: 192.168.0.0 ~ 192.168.255.255
2. Network ip
IP & Mask ==> 子网号 (不能全为0 或 全为1)
IP & (~Mask) ==> 主机号 (不能全为0 或 全为1)
Example1:
在 192.168.0.0 , 255.255.255.0 的网段中，
网络号是: 192.168.0.0
广播地址是: 192.168.0.255
主机地址是: 192.168.0.1 ~ 192.168.0.254
2^8 - 2 = 256 - 2 = 254 个主机地址。
Example2:
在 192.168.92.70 , 255.255.255.0 的网段中，
网络号是: 192.168.92.0
广播地址是: 192.168.92.255
主机地址是: 192.168.92.1 ~ 192.168.92.254
2^8 - 2 = 256 - 2 = 254 个主机地址。
Example3:
A网段: 192.168.1.2 , 255.255.255.128
B网段: 192.168.1.129 , 255.255.255.128
192.168.1.2 –> 192.168.1.00000010
192.168.1.129 –> 192.168.1.10000001
192.168.1.128 –> 192.168.1.10000000
因为A和B的前25位是不一样的，所以A和B是不同的网段，即子网号是不一样的。
3. code
checkip.h
#ifndef CHECKIP
#define CHECKIP
enum EIPMSG {
EVALID,
EINVALID_IPADDRESS,
EINVALID_IPMASK,
EINVALID_NETWORKID,
EINVALID_HOSTID,
EINVALID_LOOPBACK_ADDRESS,
EINVALID_NOT_ABC
};
void g_vIPDeleteZero(char *pc);
bool g_bIPAddressIsValid(const char *pcIPAddress, long long& llIp);
bool g_bIsIPmaskValid(const char *pcIPMask, long long& llMask);
int g_iIpAndMaskIsValid(const char * pcIPAddress, const char * pcIPMask);
bool g_bInTheSameLAN(const char * pcIPAddr1, const char * pcIPMask1,
const char * pcIPAddr2, const char * pcIPMask2);
#endif
checkip.cpp
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "checkip.h"
const int MIN_IP_LEN = 7;
const int MAX_IP_LEN = 15;
bool g_bIsValidIPString(const char * pc)
{
int iLen = strlen(pc);
if(iLen<MIN_IP_LEN || iLen>MAX_IP_LEN)
{
return false;
}
bool bCurrentIsDigit = false;
bool bCurrentIsDot = false;
int iNum = 0;
for (int i=0; i<iLen; i++)
{
if( isdigit(pc[i]) )
{
iNum = iNum*10 + (pc[i]-'0');
if(iNum > 255)
{
return false;
}
bCurrentIsDigit = true;
bCurrentIsDot = false;
}
else if( pc[i] == '.' )
{
if(!bCurrentIsDigit || bCurrentIsDot)
{
return false;
}
bCurrentIsDigit = false;
bCurrentIsDot = true;
iNum = 0;
}
else
{
return false;
}
}
if(bCurrentIsDot)
{
return false;
}
return true;
}
//example:
//Input: 00.007.000.01 Output: 0.7.0.1
void g_vIPDeleteZero(char *pc)
{
char ac[100] = {0};
strcpy(ac, pc);
int iLen = strlen(ac);
char *pcTemp = &ac[0];
char *pcFound = NULL;
int i;
int j;
for (i=0; pcTemp[i] != '\0'; i++)
{
if(pcTemp[i] == '0')
{
if((i+1<3) && isdigit(pcTemp[i+1]))
{
pcTemp[i] = 'f';
}
}
else
{
pcFound = strchr(pcTemp, '.');
if(pcFound != NULL)
{
pcTemp = pcFound + 1;
i = -1;
}
else
{
break;
}
}
}
for (i=0, j=0; i<iLen; )
{
if(ac[i] != 'f')
{
pc[j++] = ac[i++];
}
else
{
i++;
}
}
pc[j] = '\0';
}
void g_vIPchar2Int(const char *pc, long long & ll)
{
ll = 0;
char ac[1024] = {0};
strcpy(ac, pc);
int iTemp;
char acTemp[100] = {0};
char * pcHead = &ac[0];
char * pcFind = strchr(ac, '.');
while(pcFind != NULL)
{
*pcFind = '\0';
strcpy(acTemp, pcHead);
pcFind++;
pcHead = pcFind;
iTemp = atoi(acTemp);
ll = (ll + (long long)iTemp) * 256;
pcFind = strchr(pcHead, '.');
}
strcpy(acTemp, pcHead);
iTemp = atoi(acTemp);
ll = ll + (long long)iTemp;
}
bool g_bIPAddressIsValid(const char *pcIPAddress, long long& llIp)
{
if( !g_bIsValidIPString(pcIPAddress) )
{
return false;
}
g_vIPchar2Int(pcIPAddress, llIp);
if((llIp==0) || (llIp==0xffffffff))
{
return false;
}
else
{
return true;
}
}
bool g_bIsIPmaskValid(const char *pcIPMask, long long& llMask)
{
if( !g_bIsValidIPString(pcIPMask) )
{
return false;
}
g_vIPchar2Int(pcIPMask, llMask);
if((llMask|(llMask-1)) == 0xffffffff)
{
return true;
}
else
{
return false;
}
}
int g_iIpAndMaskIsValid(const char * pcIPAddress, const char * pcIPMask)
{
long long llIp = 0;
long long llMask = 0;
if(!g_bIPAddressIsValid(pcIPAddress, llIp))
{
return EINVALID_IPADDRESS;
}
if(!g_bIsIPmaskValid(pcIPMask, llMask))
{
return EINVALID_IPMASK;
}
int iHead = (llIp & 0xff000000) >> 24;
if(iHead == 127)
{
return EINVALID_LOOPBACK_ADDRESS;
}
if( !(iHead>0 && iHead<=223) )
{
return EINVALID_NOT_ABC;
}
long long llNet = llIp & llMask;
if(llNet==0 || llNet==llMask)
{
return EINVALID_NETWORKID;
}
long long llHost = llIp & (~llMask);
if(llHost==0 || llHost==((~llMask)&0xffffff))
{
return EINVALID_HOSTID;
}
return EVALID;
}
bool g_bInTheSameLAN(const char * pcIPAddr1, const char * pcIPMask1,
const char * pcIPAddr2, const char * pcIPMask2)
{
long long llIPAddr1 = 0;
long long llIPMask1 = 0;
long long llIPAddr2 = 0;
long long llIPMask2 = 0;
if( (!g_bIPAddressIsValid(pcIPAddr1, llIPAddr1)) ||
(!g_bIsIPmaskValid(pcIPMask1, llIPMask1)) ||
(!g_bIPAddressIsValid(pcIPAddr2, llIPAddr2)) ||
(!g_bIsIPmaskValid(pcIPMask2, llIPMask2)) )
{
return false;
}
long long llNet1 = llIPAddr1 & llIPMask1;
long long llNet2 = llIPAddr2 & llIPMask2;
return llNet1 == llNet2;
}
