函式原型：

#include <arpa/inet.h>

const char *inet_ntop(int af, const void *src, char *dst, socklen_t size);   //"network to printable"

int inet_pton(int af, const char *src, void *dst);

一个使用例子：
char str[INET6_ADDRSTRLEN];

if(inet_ntop(AF_INET6, &sin6_addr, str, INET6_ADDRSTRLEN) == NULL){

    perror("inet ntop/n");

    printf("error\n");

}

syslog(LOG_ERR, "sin6_addr=%s\n", str);

printf("sin6_addr=%s\n", str);        

// IPv6 demo of inet_ntop() and inet_pton()

// (basically the same except with a bunch of 6s thrown around)

struct sockaddr_in6 sa;

char str[INET6_ADDRSTRLEN];

// store this IP address in sa:

inet_pton(AF_INET6, "2001:db8:8714:3a90::12", &(sa.sin6_addr));

// now get it back and print it

inet_ntop(AF_INET6, &(sa.sin6_addr), str, INET6_ADDRSTRLEN);

printf("%s\n", str); // prints "2001:db8:8714:3a90::12"

// Helper function you can use:

//Convert a struct sockaddr address to a string, IPv4 and IPv6:

char *get_ip_str(const struct sockaddr *sa, char *s, size_t maxlen)

{

    switch(sa->sa_family) {

        case AF_INET:

            inet_ntop(AF_INET, &(((struct sockaddr_in *)sa)->sin_addr),

                    s, maxlen);

            break;

        case AF_INET6:

            inet_ntop(AF_INET6, &(((struct sockaddr_in6 *)sa)->sin6_addr),

                    s, maxlen);

            break;

        default:

            strncpy(s, "Unknown AF", maxlen);

            return NULL;

    }

    return s;

}