socket编程之地址转换函数

地址转换函数：在ASCII地址字符串（IPv4的点分十进制或IPv6的格式）与网络字节序的二进制值之间的转换

   

a:ASCILL n:network

//inet_aton/inet_addr/inet_ntoa 适用于IPv4

int inet_aton(const char *cp, struct in_addr *inp);

返回值：成功(cp有效)返回1，否则为0

注意：如果inp为NULL,对cp依然做有效性检查，但不存储结果。

in_addr_t inet_addr(const char *cp);

返回值：成功(cp有效)返回32位二进制IPv4地址，否则返回INADDR_NONE（通常情况下为常值0xffffffff，但在某些编译器中为常值-1）

注意：当解析到的IP地址本来就是255.255.255.255时，与失败返回值冲突。

char *inet_ntoa(struct in_addr in);

返回值：返回指向一个点分十进制字符串的指针

//inet_pton/inet_ntop    适用于IPv4和IPv6

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

返回值：成功返回1，cp无效或与af不对应返回0，出错(af不支持的地址族)返回-1

const char *inet_ntop(int af, const void *src, char *dst, socklen_t size);

返回值：成功返回指向一个ASCII地址字符串的指针，出错(af不支持的地址族)返回NULL

#include <stdio.h>
#include <strings.h>
#include <arpa/inet.h>
#include <netinet/in.h>

int main(void)
{
    int ret = 0;
    struct sockaddr_in addr_in;
    char *str = NULL;
    char str_addr[256] = { 0 };
    char *ip_string = "10.240.197.172";
    unsigned int ip_int = 0xacc5f00a;

    /* inet_aton */
    addr_in.sin_addr.s_addr = 0;
    ret = inet_aton(ip_string, &addr_in.sin_addr);
    printf("inet_aton 000, ret = %d, addr = %x\n",ret, addr_in.sin_addr.s_addr);

    addr_in.sin_addr.s_addr = 0;
    ret = inet_aton(ip_string, NULL);
    printf("inet_aton 111, ret = %d, addr = %x\n",ret, addr_in.sin_addr.s_addr);

    addr_in.sin_addr.s_addr = 0;
    ret = inet_aton("aaa", &addr_in.sin_addr);
    printf("inet_aton 222, ret = %d, addr = %x\n",ret, addr_in.sin_addr.s_addr);

    /* inet_addr */
    addr_in.sin_addr.s_addr = 0;
    addr_in.sin_addr.s_addr = inet_addr("aaa");
    printf("inet_addr aaa, addr = %x\n", addr_in.sin_addr.s_addr);

    addr_in.sin_addr.s_addr = 0;
    addr_in.sin_addr.s_addr = inet_addr(ip_string);
    printf("inet_addr bbb, addr = %x\n", addr_in.sin_addr.s_addr);

    /* inet_ntoa */
    addr_in.sin_addr.s_addr = 123;
    str = inet_ntoa(addr_in.sin_addr);
    printf("inet_ntoa 333, addr = %s\n", str);

    addr_in.sin_addr.s_addr = ip_int;
    str = inet_ntoa(addr_in.sin_addr);
    printf("inet_ntoa 444, addr = %s\n", str);

    /* inet_pton */
    addr_in.sin_addr.s_addr = 0;
    ret = inet_pton(AF_INET, ip_string, &addr_in.sin_addr);
    printf("inet_pton ccc, ret = %d, addr = %x\n",ret, addr_in.sin_addr.s_addr);

    addr_in.sin_addr.s_addr = 0;
    ret = inet_pton(AF_INET, "aaa", &addr_in.sin_addr);
    printf("inet_pton ddd, ret = %d, addr = %x\n",ret, addr_in.sin_addr.s_addr);

    addr_in.sin_addr.s_addr = 0;
    ret = inet_pton(AF_INET6, ip_string, &addr_in.sin_addr);
    printf("inet_pton eee, ret = %d, addr = %x\n",ret, addr_in.sin_addr.s_addr);

    addr_in.sin_addr.s_addr = 0;
    ret = inet_pton(AF_LOCAL, ip_string, &addr_in.sin_addr);
    printf("inet_pton fff, ret = %d, addr = %x\n", ret, addr_in.sin_addr.s_addr);

    /* inet_ntop */
    addr_in.sin_addr.s_addr = ip_int;
    str = (char *)inet_ntop(AF_INET, &addr_in.sin_addr, str_addr, INET_ADDRSTRLEN);
    printf("inet_ntop 555, str = %s, addr = %s\n", str, str_addr);

    bzero(str_addr, 256);
    str = (char *)inet_ntop(AF_INET6, &addr_in.sin_addr, str_addr, INET6_ADDRSTRLEN);
    printf("inet_ntop 666, str = %s, addr = %s\n", str, str_addr);

    bzero(str_addr, 256);
    str = (char *)inet_ntop(AF_LOCAL, &addr_in.sin_addr, str_addr, INET_ADDRSTRLEN);
    printf("inet_ntop 777, str = %s, addr = %s\n", str, str_addr);

    return;
}

--result

inet_aton 000, ret = 1, addr = acc5f00a

inet_aton 111, ret = 1, addr = 0

inet_aton 222, ret = 0, addr = 0

inet_addr aaa, addr = ffffffff

inet_addr bbb, addr = acc5f00a

inet_ntoa 333, addr = 123.0.0.0

inet_ntoa 444, addr = 10.240.197.172

inet_pton ccc, ret = 1, addr = acc5f00a

inet_pton ddd, ret = 0, addr = 0

inet_pton eee, ret = 0, addr = 0

inet_pton fff, ret = -1, addr = 0

inet_ntop 555, str = 10.240.197.172, addr = 10.240.197.172

inet_ntop 666, str = af0:c5ac:850a:4000::a0fb:a02a, addr = af0:c5ac:850a:4000::a0fb:a02a

inet_ntop 777, str = (null), addr =