CODEWITHSUNDEEP
c++network-programming
reza
reza

Reputation: 6358

comparing 2 IP address in string format in C

not sure what I am missing. I am trying to determine if an IP address 172.27.12.32 falls in the range of IP address 20.0.0.0 and 255.255.252.0

What I am doing is the following:

std::string one("200.0.0.0");
std::string two("172.27.12.32");
std::string three("255.255.255.255");

long one_addr = inet_addr(one.c_str());
long two_addr = inet_addr(two.c_str());
long three_addr = inet_addr(three.c_str());

one_addr is equal to 200 two_addr is equal to 537664428 three_addr is equal to 4294967295

two_addr is greater than one_addr but 172.27.12.32 is not in the range if the min IP address is 200.0.0.0

How do I determine if 172.27.12.32 is not in range of 200.0.0.0 and 255.255.255.255?

Upvotes: 0

Views: 3804

Answers (2)

Alex Reynolds
Alex Reynolds

Reputation: 96937

The inet_addr() function returns an in_addr_t struct instance:

in_addr_t inet_addr(const char *cp);

This is often a typedef for a 32-bit integer, which is not always a long on every architecture.

In any case, consider converting 20.0.0.0 and 255.255.252.0 to in_addr_t values. Then compare those results with your value of interest. What would you expect?

Upvotes: 0

evilruff
evilruff

Reputation: 4085

Hint: =) (http://www.stev.org/post/2012/08/09/C++-Check-an-IP-Address-is-in-a-IPMask-range.aspx)

uint32_t IPToUInt(const std::string ip) {
    int a, b, c, d;
    uint32_t addr = 0;

    if (sscanf(ip.c_str(), "%d.%d.%d.%d", &a, &b, &c, &d) != 4)
       return 0;

    addr = a << 24;
    addr |= b << 16;
    addr |= c << 8;
    addr |= d;
    return addr;
}

Hope thats enough to answer your question

Upvotes: 4

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