UNPv13：#第3章#套接字编程简介

#include <netinet/in.h>  

struct sockaddr_in  
{  
    uint8_t         sin_len;  
    sa_family_t     sin_family;  
    in_port_t       sin_port;  
    struct in_addr  sin_addr;  
    ...  
}; 

#include <sys/socket.h>

struct sockaddr
{
    uint8_t      sa_len;
    sa_family_t  sa_family;
    char         sa_data[14];
};

#include <netinet/in.h>

uint16_t htons(uint16_t host16bitvalue);  
uint32_t htonl(uint32_t host32bitvalue);  
uint16_t ntohs(uint16_t net16bitvalue);  
uint32_t ntohl(uint32_t net32bitvalue); 

#include <arpa/inet.h>  

int inet_aton(const char* strptr, struct in_addr* addrptr);//字符串有效返回1，否则为0
in_addr_t inet_addr(const char* strptr);//字符串有效返回网络字节序的32位IPv4地址，否则为INADDR_NONE
char* inet_ntoa(struct in_addr inaddr);//指向一个点分十进制数串的指针

#include <arpa/inet.h> 

int inet_pton(int family, const char* strptr, void* addrptr);//成功：1；输入格式无效：0；出错：-1
const char* inet_ntop(int family, const void* addrptr, char* strptr, size_t len);//失败：NULL；成功：结果

#include <netinet.in.h>

#define INET_ADDRSTRLEN 16