1、struct  in_addr

struct  in_addr就是32位IP地址。  

struct  in_addr {  union {struct { u_char s_b1,s_b2,s_b3,s_b4; } S_un_b;struct { u_short s_w1,s_w2; } S_un_w;u_long S_addr;} S_un;#define s_addr  S_un.S_addr
};  

 

 

2、sockaddr_in

struct  sockaddr_in   {  short   int   sin_family;     unsigned   short   int   sin_port;     struct   in_addr   sin_addr;     unsigned   char   sin_zero[8];     
}; 

 

sockaddr_in 结构体里面包含结构体in_addr,这是他们的关系

 

 inet_addr()是将一个点分制的IP地址(如192.168.0.1)转换为上述结构中需要的32位IP地址(0xC0A80001)

一般用法

 

struct  sockaddr_in   sockaddr;  
sockaddr.sin_family   =   AF_INET;     
sockaddr.sin_port   =   htons(MYPORT);     
sockaddr.sin_addr.s_addr   =   inet_addr("192.168.0.1");