hostent h_addr_list

96 阅读 0 评论 64 点赞

我是靠谱客的博主甜甜水杯，这篇文章主要介绍hostent h_addr_list，现在分享给大家，希望可以做个参考。

复制代码

1
2
3
4
5
6
7
8
struct  hostent {
        char    FAR * h_name;           /* official name of host */
        char    FAR * FAR * h_aliases;  /* alias list */
        short   h_addrtype;             /* host address type */
        short   h_length;               /* length of address */
        char    FAR * FAR * h_addr_list; /* list of addresses */
#define h_addr  h_addr_list[0]          /* address, for backward compat */
};

h_addr_list其实是一个指针数组，数组中每个元素都是in_addr型指针。

复制代码

1
2
3
4
5
6
7
8
9
10
11
12
13
typedef struct in_addr {
        union {
                struct { UCHAR s_b1,s_b2,s_b3,s_b4; } S_un_b;
                struct { USHORT s_w1,s_w2; } S_un_w;
                ULONG S_addr;
        } S_un;
#define s_addr  S_un.S_addr /* can be used for most tcp & ip code */
#define s_host  S_un.S_un_b.s_b2    // host on imp
#define s_net   S_un.S_un_b.s_b1    // network
#define s_imp   S_un.S_un_w.s_w2    // imp
#define s_impno S_un.S_un_b.s_b4    // imp #
#define s_lh    S_un.S_un_b.s_b3    // logical host
} IN_ADDR, *PIN_ADDR, FAR *LPIN_ADDR;

因为hostent结构支持多种地址类型，所以其定义的h_addr_list是char **型。gethostbyname以后，实际存储情况是这样：

复制代码

1
2
3
4
hostent->h_addr_list[0][0] = 127
hostent->h_addr_list[0][1] = 0
hostent->h_addr_list[0][2] = 0
hostent->h_addr_list[0][3] = 1

得到的地址是网络字节顺序。转成正常的字符：

复制代码

1
2
3
char *ip;
ip = inet_ntoa(*(struct in_addr *)*phost->h_addr_list);

向sockaddr_in赋值：

复制代码

1
2
3
4
5
struct sockaddr whereto;
struct sockaddr_in *to;
memset(&whereto, 0, sizeof(struct sockaddr));
to = (struct sockaddr_in *)&whereto;
memcpy(&to->sin_addr, hp->h_addr, hp->h_length);