为什么网络程序将IP地址存储在IP地址结构中

Question

I'm a beginner in C, my textbooks cover some network programming in C, and states that Network programs store IP addresses in the IP address structure

/* Internet address structure */
struct in_addr {
unsigned int s_addr; /* Network byte order (big-endian) */
};

I'm confused, can't we just store a 32 bit integer?

Answer 1

in_addr represents an IPv4 address, which can indeed fit in a 32bit integer.

But, there are other types of socket addresses that cannot, such as IPv6 addresses.

Each type of socket address uses its own struct type:

• in_addr for IPv4
• in6_addr for IPv6
• char[] for UNIX paths
• etc

Usually wrapped inside a corresponding sockaddr struct:

• sockaddr_in for IPv4
• sockaddr_in6 for IPv6
• sockaddr_un for UNIX
• etc

Which is what you use with socket APIs like bind() , connect() , accept() , sendto() , recvfrom() , etc.

Very rarely would you ever need to use something like in_addr directly by itself. Typically you would use it in conjunction with an API that requires an IPv4 address to be passed via the in_addr struct.