
:mod:`BaseHTTPServer` --- Basic HTTP server
===========================================

.. module:: BaseHTTPServer
   :synopsis: Basic HTTP server (base class for SimpleHTTPServer and CGIHTTPServer).


.. index::
   pair: WWW; server
   pair: HTTP; protocol
   single: URL
   single: httpd

.. index::
   module: SimpleHTTPServer
   module: CGIHTTPServer

This module defines two classes for implementing HTTP servers (Web servers).
Usually, this module isn't used directly, but is used as a basis for building
functioning Web servers. See the :mod:`SimpleHTTPServer` and
:mod:`CGIHTTPServer` modules.

The first class, :class:`HTTPServer`, is a :class:`socketserver.TCPServer`
subclass.  It creates and listens at the HTTP socket, dispatching the requests
to a handler.  Code to create and run the server looks like this::

   def run(server_class=BaseHTTPServer.HTTPServer,
           handler_class=BaseHTTPServer.BaseHTTPRequestHandler):
       server_address = ('', 8000)
       httpd = server_class(server_address, handler_class)
       httpd.serve_forever()


.. class:: HTTPServer(server_address, RequestHandlerClass)

   This class builds on the :class:`TCPServer` class by storing the server
   address as instance variables named :attr:`server_name` and
   :attr:`server_port`. The server is accessible by the handler, typically
   through the handler's :attr:`server` instance variable.


.. class:: BaseHTTPRequestHandler(request, client_address, server)

   This class is used to handle the HTTP requests that arrive at the server. By
   itself, it cannot respond to any actual HTTP requests; it must be subclassed
   to handle each request method (e.g. GET or
   POST). :class:`BaseHTTPRequestHandler` provides a number of class and
   instance variables, and methods for use by subclasses.

   The handler will parse the request and the headers, then call a method
   specific to the request type. The method name is constructed from the
   request. For example, for the request method ``SPAM``, the :meth:`do_SPAM`
   method will be called with no arguments. All of the relevant information is
   stored in instance variables of the handler.  Subclasses should not need to
   override or extend the :meth:`__init__` method.

   :class:`BaseHTTPRequestHandler` has the following instance variables:


   .. attribute:: client_address

      Contains a tuple of the form ``(host, port)`` referring to the client's
      address.


   .. attribute:: command

      Contains the command (request type). For example, ``'GET'``.


   .. attribute:: path

      Contains the request path.


   .. attribute:: request_version

      Contains the version string from the request. For example, ``'HTTP/1.0'``.


   .. attribute:: headers

      Holds an instance of the class specified by the :attr:`MessageClass` class
      variable. This instance parses and manages the headers in the HTTP
      request.


   .. attribute:: rfile

      Contains an input stream, positioned at the start of the optional input
      data.


   .. attribute:: wfile

      Contains the output stream for writing a response back to the
      client. Proper adherence to the HTTP protocol must be used when writing to
      this stream.


   :class:`BaseHTTPRequestHandler` has the following class variables:


   .. attribute:: server_version

      Specifies the server software version.  You may want to override this. The
      format is multiple whitespace-separated strings, where each string is of
      the form name[/version]. For example, ``'BaseHTTP/0.2'``.


   .. attribute:: sys_version

      Contains the Python system version, in a form usable by the
      :attr:`version_string` method and the :attr:`server_version` class
      variable. For example, ``'Python/1.4'``.


   .. attribute:: error_message_format

      Specifies a format string for building an error response to the client. It
      uses parenthesized, keyed format specifiers, so the format operand must be
      a dictionary. The *code* key should be an integer, specifying the numeric
      HTTP error code value. *message* should be a string containing a
      (detailed) error message of what occurred, and *explain* should be an
      explanation of the error code number. Default *message* and *explain*
      values can found in the *responses* class variable.


   .. attribute:: error_content_type

      Specifies the Content-Type HTTP header of error responses sent to the
      client.  The default value is ``'text/html'``.


   .. attribute:: protocol_version

      This specifies the HTTP protocol version used in responses.  If set to
      ``'HTTP/1.1'``, the server will permit HTTP persistent connections;
      however, your server *must* then include an accurate ``Content-Length``
      header (using :meth:`send_header`) in all of its responses to clients.
      For backwards compatibility, the setting defaults to ``'HTTP/1.0'``.


   .. attribute:: MessageClass

      .. index:: single: Message (in module mimetools)

      Specifies a :class:`rfc822.Message`\ -like class to parse HTTP headers.
      Typically, this is not overridden, and it defaults to
      :class:`mimetools.Message`.


   .. attribute:: responses

      This variable contains a mapping of error code integers to two-element tuples
      containing a short and long message. For example, ``{code: (shortmessage,
      longmessage)}``. The *shortmessage* is usually used as the *message* key in an
      error response, and *longmessage* as the *explain* key (see the
      :attr:`error_message_format` class variable).


   A :class:`BaseHTTPRequestHandler` instance has the following methods:


   .. method:: handle()

      Calls :meth:`handle_one_request` once (or, if persistent connections are
      enabled, multiple times) to handle incoming HTTP requests. You should
      never need to override it; instead, implement appropriate :meth:`do_\*`
      methods.


   .. method:: handle_one_request()

      This method will parse and dispatch the request to the appropriate
      :meth:`do_\*` method.  You should never need to override it.


   .. method:: send_error(code[, message])

      Sends and logs a complete error reply to the client. The numeric *code*
      specifies the HTTP error code, with *message* as optional, more specific text. A
      complete set of headers is sent, followed by text composed using the
      :attr:`error_message_format` class variable.


   .. method:: send_response(code[, message])

      Sends a response header and logs the accepted request. The HTTP response
      line is sent, followed by *Server* and *Date* headers. The values for
      these two headers are picked up from the :meth:`version_string` and
      :meth:`date_time_string` methods, respectively.


   .. method:: send_header(keyword, value)

      Writes a specific HTTP header to the output stream. *keyword* should
      specify the header keyword, with *value* specifying its value.


   .. method:: end_headers()

      Sends a blank line, indicating the end of the HTTP headers in the
      response.


   .. method:: log_request([code[, size]])

      Logs an accepted (successful) request. *code* should specify the numeric
      HTTP code associated with the response. If a size of the response is
      available, then it should be passed as the *size* parameter.


   .. method:: log_error(...)

      Logs an error when a request cannot be fulfilled. By default, it passes
      the message to :meth:`log_message`, so it takes the same arguments
      (*format* and additional values).


   .. method:: log_message(format, ...)

      Logs an arbitrary message to ``sys.stderr``. This is typically overridden
      to create custom error logging mechanisms. The *format* argument is a
      standard printf-style format string, where the additional arguments to
      :meth:`log_message` are applied as inputs to the formatting. The client
      address and current date and time are prefixed to every message logged.


   .. method:: version_string()

      Returns the server software's version string. This is a combination of the
      :attr:`server_version` and :attr:`sys_version` class variables.


   .. method:: date_time_string([timestamp])

      Returns the date and time given by *timestamp* (which must be in the
      format returned by :func:`time.time`), formatted for a message header. If
      *timestamp* is omitted, it uses the current date and time.

      The result looks like ``'Sun, 06 Nov 1994 08:49:37 GMT'``.


   .. method:: log_date_time_string()

      Returns the current date and time, formatted for logging.


   .. method:: address_string()

      Returns the client address, formatted for logging. A name lookup is
      performed on the client's IP address.


.. seealso::

   Module :mod:`CGIHTTPServer`
      Extended request handler that supports CGI scripts.

   Module :mod:`SimpleHTTPServer`
      Basic request handler that limits response to files actually under the document
      root.

