class BaseHTTPRequestHandler(socketserver.StreamRequestHandler)

 HTTP request handler base class.
 |  
 |  The following explanation of HTTP serves to guide you through the
 |  code as well as to expose any misunderstandings I may have about
 |  HTTP (so you don‘t need to read the code to figure out I‘m wrong
 |  :-).
 |  
 |  HTTP (HyperText Transfer Protocol) is an extensible protocol on
 |  top of a reliable stream transport (e.g. TCP/IP).  The protocol
 |  recognizes three parts to a request:
 |  
 |  1. One line identifying the request type and path
 |  2. An optional set of RFC-822-style headers
 |  3. An optional data part
 |  
 |  The headers and data are separated by a blank line.
 |  
 |  The first line of the request has the form
 |  
 |  <command> <path> <version>
 |  
 |  where <command> is a (case-sensitive) keyword such as GET or POST,
 |  <path> is a string containing path information for the request,
 |  and <version> should be the string "HTTP/1.0" or "HTTP/1.1".
 |  <path> is encoded using the URL encoding scheme (using %xx to signify
 |  the ASCII character with hex code xx).
 |  
 |  The specification specifies that lines are separated by CRLF but
 |  for compatibility with the widest range of clients recommends
 |  servers also handle LF.  Similarly, whitespace in the request line
 |  is treated sensibly (allowing multiple spaces between components
 |  and allowing trailing whitespace).
 |  
 |  Similarly, for output, lines ought to be separated by CRLF pairs
 |  but most clients grok LF characters just fine.
 |  
 |  If the first line of the request has the form

 |  <command> <path>
 |  
 |  (i.e. <version> is left out) then this is assumed to be an HTTP
 |  0.9 request; this form has no optional headers and data part and
 |  the reply consists of just the data.
 |  
 |  The reply form of the HTTP 1.x protocol again has three parts:
 |  
 |  1. One line giving the response code
 |  2. An optional set of RFC-822-style headers
 |  3. The data
 |  
 |  Again, the headers and data are separated by a blank line.
 |  
 |  The response code line has the form
 |  
 |  <version> <responsecode> <responsestring>
 |  
 |  where <version> is the protocol version ("HTTP/1.0" or "HTTP/1.1"),
 |  <responsecode> is a 3-digit response code indicating success or
 |  failure of the request, and <responsestring> is an optional
 |  human-readable string explaining what the response code means.
 |  
 |  This server parses the request and the headers, and then calls a
 |  function specific to the request type (<command>).  Specifically,
 |  a request SPAM will be handled by a method do_SPAM().  If no
 |  such method exists the server sends an error response to the
 |  client.  If it exists, it is called with no arguments:
 |  
 |  do_SPAM()
 |  
 |  Note that the request name is case sensitive (i.e. SPAM and spam
 |  are different requests).
 
 |  The various request details are stored in instance variables:
 |  
 |  - client_address is the client IP address in the form (host,
 |  port);
 |  
 |  - command, path and version are the broken-down request line;
 |  
 |  - headers is an instance of email.message.Message (or a derived
 |  class) containing the header information;
 |  
 |  - rfile is a file object open for reading positioned at the
 |  start of the optional input data part;
 |  
 |  - wfile is a file object open for writing.
 |  
 |  IT IS IMPORTANT TO ADHERE TO THE PROTOCOL FOR WRITING!
 |  
 |  The first thing to be written must be the response line.  Then
 |  follow 0 or more header lines, then a blank line, and then the
 |  actual data (if any).  The meaning of the header lines depends on
 |  the command executed by the server; in most cases, when data is
 |  returned, there should be at least one header line of the form
 |  
 |  Content-type: <type>/<subtype>
 |  
 |  where <type> and <subtype> should be registered MIME types,
 |  e.g. "text/html" or "text/plain".
 |  
 |  Method resolution order:
 |      BaseHTTPRequestHandler
 |      socketserver.StreamRequestHandler
 |      socketserver.BaseRequestHandler
 |      builtins.object

Python——Baseequestandler class （Interesting found in python‘s document）