Principle of second-level domain name Management System

Many second-level domain names are used on the Internet. How does one implement it? In fact, it is very easy to say.
1. a wildcard domain name is required. Make a resolution: * .domain.com; it means to resolve all domain names suffixed with domain.com to the specified IP address;

2. It must be a host because the second-level domain name management system must be installed on the default website. Because only one host is allowed.

3. a domain name management system. The default homepage is usually default. asp. In a common website, This is the homepage. But in the second-level domain name management system. This is an analysisProgram. Working principle:
1) receive the URL pointing to the default website;
2) analyze the URL data to see if it has been registered;
3) if the domain name is registered, extract the second-level domain name specified by the user from the database and then open it;