DNS (Domain Name System) Back

• 作用: IP地址的別名, 便於記憶
• 結構: 域名層次樹

• 存放: 域名服務器
  • 存放域名和IP的對應記錄
  • 提供域名查詢功能

域名訪問

• 域名與IP的互相轉換

1. 域名到IP的轉換

• 對同一個DNS服務器兩次調用所返回的IP地址列表順序有可能不同.
• 在不同的DNS服務器上查詢, 返回結果不同.
• 查詢失敗時, 可以通過hstrerror()查找h_errno的信息.
• 由於查詢是逐級的, 建議採用多進程(線程)來縮短時間消耗.

方法

struct hostent* gethostbyname(const char* name)

/* hostent */
struct hostent
{
    char h_name;    //host name
    char** h_aliases;    //alias list, with NULL ends
    int h_addrtype;    //types of host address: AF_INET
    int h_length;    //length of host address: 32 bits
    char** h_addr_list;    //host address list, with NULL ends
}

参数

• name: 域名

2. IP到域名的轉換

方法

struct hostent* gethostbyaddr(const char* addr, size_t len, int family)

/* hostent */
struct hostent
{
    char h_name;    //host name
    char** h_aliases;    //alias list, with NULL ends
    int h_addrtype;    //types of host address: AF_INET
    int h_length;    //length of host address: 32 bits
    char** h_addr_list;    //host address list, with NULL ends
}

参数

• addr: 地址
• len: 地址長度
• family: 地址的協議簇

Comments Copyright © aleen42 all right reserved, powered by aleen42

Empty Comments

Sign in GitHub

As the plugin is integrated with a code management system like GitLab or GitHub, you may have to auth with your account before leaving comments around this article.

Notice: This plugin has used Cookie to store your token with an expiration.

authorize