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564 lines
21 KiB
ReStructuredText
564 lines
21 KiB
ReStructuredText
:mod:`!http.server` --- HTTP servers
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====================================
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.. module:: http.server
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:synopsis: HTTP server and request handlers.
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**Source code:** :source:`Lib/http/server.py`
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.. index::
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pair: WWW; server
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pair: HTTP; protocol
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single: URL
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single: httpd
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--------------
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This module defines classes for implementing HTTP servers.
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.. warning::
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:mod:`http.server` is not recommended for production. It only implements
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:ref:`basic security checks <http.server-security>`.
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.. include:: ../includes/wasm-notavail.rst
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One class, :class:`HTTPServer`, is a :class:`socketserver.TCPServer` subclass.
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It creates and listens at the HTTP socket, dispatching the requests to a
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handler. Code to create and run the server looks like this::
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def run(server_class=HTTPServer, handler_class=BaseHTTPRequestHandler):
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server_address = ('', 8000)
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httpd = server_class(server_address, handler_class)
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httpd.serve_forever()
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.. class:: HTTPServer(server_address, RequestHandlerClass)
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This class builds on the :class:`~socketserver.TCPServer` class by storing
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the server address as instance variables named :attr:`server_name` and
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:attr:`server_port`. The server is accessible by the handler, typically
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through the handler's :attr:`server` instance variable.
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.. class:: ThreadingHTTPServer(server_address, RequestHandlerClass)
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This class is identical to HTTPServer but uses threads to handle
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requests by using the :class:`~socketserver.ThreadingMixIn`. This
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is useful to handle web browsers pre-opening sockets, on which
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:class:`HTTPServer` would wait indefinitely.
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.. versionadded:: 3.7
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The :class:`HTTPServer` and :class:`ThreadingHTTPServer` must be given
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a *RequestHandlerClass* on instantiation, of which this module
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provides three different variants:
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.. class:: BaseHTTPRequestHandler(request, client_address, server)
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This class is used to handle the HTTP requests that arrive at the server. By
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itself, it cannot respond to any actual HTTP requests; it must be subclassed
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to handle each request method (e.g. GET or POST).
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:class:`BaseHTTPRequestHandler` provides a number of class and instance
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variables, and methods for use by subclasses.
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The handler will parse the request and the headers, then call a method
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specific to the request type. The method name is constructed from the
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request. For example, for the request method ``SPAM``, the :meth:`!do_SPAM`
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method will be called with no arguments. All of the relevant information is
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stored in instance variables of the handler. Subclasses should not need to
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override or extend the :meth:`!__init__` method.
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:class:`BaseHTTPRequestHandler` has the following instance variables:
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.. attribute:: client_address
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Contains a tuple of the form ``(host, port)`` referring to the client's
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address.
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.. attribute:: server
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Contains the server instance.
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.. attribute:: close_connection
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Boolean that should be set before :meth:`handle_one_request` returns,
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indicating if another request may be expected, or if the connection should
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be shut down.
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.. attribute:: requestline
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Contains the string representation of the HTTP request line. The
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terminating CRLF is stripped. This attribute should be set by
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:meth:`handle_one_request`. If no valid request line was processed, it
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should be set to the empty string.
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.. attribute:: command
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Contains the command (request type). For example, ``'GET'``.
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.. attribute:: path
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Contains the request path. If query component of the URL is present,
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then ``path`` includes the query. Using the terminology of :rfc:`3986`,
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``path`` here includes ``hier-part`` and the ``query``.
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.. attribute:: request_version
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Contains the version string from the request. For example, ``'HTTP/1.0'``.
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.. attribute:: headers
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Holds an instance of the class specified by the :attr:`MessageClass` class
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variable. This instance parses and manages the headers in the HTTP
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request. The :func:`~http.client.parse_headers` function from
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:mod:`http.client` is used to parse the headers and it requires that the
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HTTP request provide a valid :rfc:`2822` style header.
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.. attribute:: rfile
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An :class:`io.BufferedIOBase` input stream, ready to read from
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the start of the optional input data.
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.. attribute:: wfile
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Contains the output stream for writing a response back to the
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client. Proper adherence to the HTTP protocol must be used when writing to
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this stream in order to achieve successful interoperation with HTTP
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clients.
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.. versionchanged:: 3.6
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This is an :class:`io.BufferedIOBase` stream.
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:class:`BaseHTTPRequestHandler` has the following attributes:
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.. attribute:: server_version
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Specifies the server software version. You may want to override this. The
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format is multiple whitespace-separated strings, where each string is of
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the form name[/version]. For example, ``'BaseHTTP/0.2'``.
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.. attribute:: sys_version
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Contains the Python system version, in a form usable by the
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:attr:`version_string` method and the :attr:`server_version` class
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variable. For example, ``'Python/1.4'``.
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.. attribute:: error_message_format
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Specifies a format string that should be used by :meth:`send_error` method
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for building an error response to the client. The string is filled by
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default with variables from :attr:`responses` based on the status code
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that passed to :meth:`send_error`.
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.. attribute:: error_content_type
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Specifies the Content-Type HTTP header of error responses sent to the
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client. The default value is ``'text/html'``.
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.. attribute:: protocol_version
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Specifies the HTTP version to which the server is conformant. It is sent
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in responses to let the client know the server's communication
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capabilities for future requests. If set to
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``'HTTP/1.1'``, the server will permit HTTP persistent connections;
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however, your server *must* then include an accurate ``Content-Length``
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header (using :meth:`send_header`) in all of its responses to clients.
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For backwards compatibility, the setting defaults to ``'HTTP/1.0'``.
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.. attribute:: MessageClass
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Specifies an :class:`email.message.Message`\ -like class to parse HTTP
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headers. Typically, this is not overridden, and it defaults to
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:class:`http.client.HTTPMessage`.
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.. attribute:: responses
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This attribute contains a mapping of error code integers to two-element tuples
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containing a short and long message. For example, ``{code: (shortmessage,
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longmessage)}``. The *shortmessage* is usually used as the *message* key in an
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error response, and *longmessage* as the *explain* key. It is used by
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:meth:`send_response_only` and :meth:`send_error` methods.
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A :class:`BaseHTTPRequestHandler` instance has the following methods:
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.. method:: handle()
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Calls :meth:`handle_one_request` once (or, if persistent connections are
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enabled, multiple times) to handle incoming HTTP requests. You should
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never need to override it; instead, implement appropriate :meth:`!do_\*`
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methods.
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.. method:: handle_one_request()
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This method will parse and dispatch the request to the appropriate
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:meth:`!do_\*` method. You should never need to override it.
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.. method:: handle_expect_100()
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When an HTTP/1.1 conformant server receives an ``Expect: 100-continue``
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request header it responds back with a ``100 Continue`` followed by ``200
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OK`` headers.
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This method can be overridden to raise an error if the server does not
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want the client to continue. For e.g. server can choose to send ``417
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Expectation Failed`` as a response header and ``return False``.
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.. versionadded:: 3.2
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.. method:: send_error(code, message=None, explain=None)
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Sends and logs a complete error reply to the client. The numeric *code*
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specifies the HTTP error code, with *message* as an optional, short, human
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readable description of the error. The *explain* argument can be used to
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provide more detailed information about the error; it will be formatted
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using the :attr:`error_message_format` attribute and emitted, after
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a complete set of headers, as the response body. The :attr:`responses`
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attribute holds the default values for *message* and *explain* that
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will be used if no value is provided; for unknown codes the default value
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for both is the string ``???``. The body will be empty if the method is
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HEAD or the response code is one of the following: :samp:`1{xx}`,
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``204 No Content``, ``205 Reset Content``, ``304 Not Modified``.
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.. versionchanged:: 3.4
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The error response includes a Content-Length header.
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Added the *explain* argument.
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.. method:: send_response(code, message=None)
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Adds a response header to the headers buffer and logs the accepted
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request. The HTTP response line is written to the internal buffer,
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followed by *Server* and *Date* headers. The values for these two headers
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are picked up from the :meth:`version_string` and
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:meth:`date_time_string` methods, respectively. If the server does not
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intend to send any other headers using the :meth:`send_header` method,
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then :meth:`send_response` should be followed by an :meth:`end_headers`
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call.
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.. versionchanged:: 3.3
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Headers are stored to an internal buffer and :meth:`end_headers`
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needs to be called explicitly.
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.. method:: send_header(keyword, value)
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Adds the HTTP header to an internal buffer which will be written to the
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output stream when either :meth:`end_headers` or :meth:`flush_headers` is
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invoked. *keyword* should specify the header keyword, with *value*
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specifying its value. Note that, after the send_header calls are done,
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:meth:`end_headers` MUST BE called in order to complete the operation.
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.. versionchanged:: 3.2
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Headers are stored in an internal buffer.
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.. method:: send_response_only(code, message=None)
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Sends the response header only, used for the purposes when ``100
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Continue`` response is sent by the server to the client. The headers not
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buffered and sent directly the output stream.If the *message* is not
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specified, the HTTP message corresponding the response *code* is sent.
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.. versionadded:: 3.2
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.. method:: end_headers()
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Adds a blank line
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(indicating the end of the HTTP headers in the response)
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to the headers buffer and calls :meth:`flush_headers`.
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.. versionchanged:: 3.2
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The buffered headers are written to the output stream.
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.. method:: flush_headers()
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Finally send the headers to the output stream and flush the internal
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headers buffer.
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.. versionadded:: 3.3
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.. method:: log_request(code='-', size='-')
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Logs an accepted (successful) request. *code* should specify the numeric
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HTTP code associated with the response. If a size of the response is
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available, then it should be passed as the *size* parameter.
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.. method:: log_error(...)
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Logs an error when a request cannot be fulfilled. By default, it passes
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the message to :meth:`log_message`, so it takes the same arguments
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(*format* and additional values).
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.. method:: log_message(format, ...)
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Logs an arbitrary message to ``sys.stderr``. This is typically overridden
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to create custom error logging mechanisms. The *format* argument is a
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standard printf-style format string, where the additional arguments to
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:meth:`log_message` are applied as inputs to the formatting. The client
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ip address and current date and time are prefixed to every message logged.
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.. method:: version_string()
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Returns the server software's version string. This is a combination of the
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:attr:`server_version` and :attr:`sys_version` attributes.
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.. method:: date_time_string(timestamp=None)
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Returns the date and time given by *timestamp* (which must be ``None`` or in
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the format returned by :func:`time.time`), formatted for a message
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header. If *timestamp* is omitted, it uses the current date and time.
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The result looks like ``'Sun, 06 Nov 1994 08:49:37 GMT'``.
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.. method:: log_date_time_string()
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Returns the current date and time, formatted for logging.
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.. method:: address_string()
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Returns the client address.
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.. versionchanged:: 3.3
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Previously, a name lookup was performed. To avoid name resolution
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delays, it now always returns the IP address.
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.. class:: SimpleHTTPRequestHandler(request, client_address, server, directory=None)
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This class serves files from the directory *directory* and below,
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or the current directory if *directory* is not provided, directly
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mapping the directory structure to HTTP requests.
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.. versionchanged:: 3.7
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Added the *directory* parameter.
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.. versionchanged:: 3.9
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The *directory* parameter accepts a :term:`path-like object`.
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A lot of the work, such as parsing the request, is done by the base class
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:class:`BaseHTTPRequestHandler`. This class implements the :func:`do_GET`
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and :func:`do_HEAD` functions.
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The following are defined as class-level attributes of
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:class:`SimpleHTTPRequestHandler`:
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.. attribute:: server_version
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This will be ``"SimpleHTTP/" + __version__``, where ``__version__`` is
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defined at the module level.
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.. attribute:: extensions_map
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A dictionary mapping suffixes into MIME types, contains custom overrides
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for the default system mappings. The mapping is used case-insensitively,
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and so should contain only lower-cased keys.
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.. versionchanged:: 3.9
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This dictionary is no longer filled with the default system mappings,
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but only contains overrides.
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The :class:`SimpleHTTPRequestHandler` class defines the following methods:
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.. method:: do_HEAD()
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This method serves the ``'HEAD'`` request type: it sends the headers it
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would send for the equivalent ``GET`` request. See the :meth:`do_GET`
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method for a more complete explanation of the possible headers.
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.. method:: do_GET()
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The request is mapped to a local file by interpreting the request as a
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path relative to the current working directory.
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If the request was mapped to a directory, the directory is checked for a
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file named ``index.html`` or ``index.htm`` (in that order). If found, the
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file's contents are returned; otherwise a directory listing is generated
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by calling the :meth:`list_directory` method. This method uses
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:func:`os.listdir` to scan the directory, and returns a ``404`` error
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response if the :func:`~os.listdir` fails.
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If the request was mapped to a file, it is opened. Any :exc:`OSError`
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exception in opening the requested file is mapped to a ``404``,
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``'File not found'`` error. If there was an ``'If-Modified-Since'``
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header in the request, and the file was not modified after this time,
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a ``304``, ``'Not Modified'`` response is sent. Otherwise, the content
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type is guessed by calling the :meth:`guess_type` method, which in turn
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uses the *extensions_map* variable, and the file contents are returned.
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A ``'Content-type:'`` header with the guessed content type is output,
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followed by a ``'Content-Length:'`` header with the file's size and a
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``'Last-Modified:'`` header with the file's modification time.
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Then follows a blank line signifying the end of the headers, and then the
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contents of the file are output. If the file's MIME type starts with
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``text/`` the file is opened in text mode; otherwise binary mode is used.
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For example usage, see the implementation of the ``test`` function
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in :source:`Lib/http/server.py`.
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.. versionchanged:: 3.7
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Support of the ``'If-Modified-Since'`` header.
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The :class:`SimpleHTTPRequestHandler` class can be used in the following
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manner in order to create a very basic webserver serving files relative to
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the current directory::
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import http.server
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import socketserver
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PORT = 8000
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Handler = http.server.SimpleHTTPRequestHandler
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with socketserver.TCPServer(("", PORT), Handler) as httpd:
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print("serving at port", PORT)
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httpd.serve_forever()
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:class:`SimpleHTTPRequestHandler` can also be subclassed to enhance behavior,
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such as using different index file names by overriding the class attribute
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:attr:`index_pages`.
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.. class:: CGIHTTPRequestHandler(request, client_address, server)
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This class is used to serve either files or output of CGI scripts from the
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current directory and below. Note that mapping HTTP hierarchic structure to
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local directory structure is exactly as in :class:`SimpleHTTPRequestHandler`.
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.. note::
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CGI scripts run by the :class:`CGIHTTPRequestHandler` class cannot execute
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redirects (HTTP code 302), because code 200 (script output follows) is
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sent prior to execution of the CGI script. This pre-empts the status
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code.
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The class will however, run the CGI script, instead of serving it as a file,
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if it guesses it to be a CGI script. Only directory-based CGI are used ---
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the other common server configuration is to treat special extensions as
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denoting CGI scripts.
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The :func:`do_GET` and :func:`do_HEAD` functions are modified to run CGI scripts
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and serve the output, instead of serving files, if the request leads to
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somewhere below the ``cgi_directories`` path.
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The :class:`CGIHTTPRequestHandler` defines the following data member:
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.. attribute:: cgi_directories
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This defaults to ``['/cgi-bin', '/htbin']`` and describes directories to
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treat as containing CGI scripts.
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The :class:`CGIHTTPRequestHandler` defines the following method:
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.. method:: do_POST()
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This method serves the ``'POST'`` request type, only allowed for CGI
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scripts. Error 501, "Can only POST to CGI scripts", is output when trying
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to POST to a non-CGI url.
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Note that CGI scripts will be run with UID of user nobody, for security
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reasons. Problems with the CGI script will be translated to error 403.
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.. deprecated-removed:: 3.13 3.15
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:class:`CGIHTTPRequestHandler` is being removed in 3.15. CGI has not
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been considered a good way to do things for well over a decade. This code
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has been unmaintained for a while now and sees very little practical use.
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Retaining it could lead to further :ref:`security considerations
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<http.server-security>`.
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.. _http-server-cli:
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Command-line interface
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----------------------
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:mod:`http.server` can also be invoked directly using the :option:`-m`
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switch of the interpreter. The following example illustrates how to serve
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files relative to the current directory::
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python -m http.server [OPTIONS] [port]
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The following options are accepted:
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.. program:: http.server
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.. option:: port
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The server listens to port 8000 by default. The default can be overridden
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by passing the desired port number as an argument::
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python -m http.server 9000
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.. option:: -b, --bind <address>
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Specifies a specific address to which it should bind. Both IPv4 and IPv6
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addresses are supported. By default, the server binds itself to all
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interfaces. For example, the following command causes the server to bind
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to localhost only::
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python -m http.server --bind 127.0.0.1
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.. versionadded:: 3.4
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.. versionchanged:: 3.8
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Support IPv6 in the ``--bind`` option.
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.. option:: -d, --directory <dir>
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Specifies a directory to which it should serve the files. By default,
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the server uses the current directory. For example, the following command
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uses a specific directory::
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python -m http.server --directory /tmp/
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.. versionadded:: 3.7
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.. option:: -p, --protocol <version>
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Specifies the HTTP version to which the server is conformant. By default,
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the server is conformant to HTTP/1.0. For example, the following command
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runs an HTTP/1.1 conformant server::
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python -m http.server --protocol HTTP/1.1
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.. versionadded:: 3.11
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.. option:: --cgi
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:class:`CGIHTTPRequestHandler` can be enabled in the command line by passing
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the ``--cgi`` option::
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python -m http.server --cgi
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.. deprecated-removed:: 3.13 3.15
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:mod:`http.server` command line ``--cgi`` support is being removed
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because :class:`CGIHTTPRequestHandler` is being removed.
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.. warning::
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:class:`CGIHTTPRequestHandler` and the ``--cgi`` command-line option
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are not intended for use by untrusted clients and may be vulnerable
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to exploitation. Always use within a secure environment.
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.. _http.server-security:
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Security considerations
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-----------------------
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.. index:: pair: http.server; security
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:class:`SimpleHTTPRequestHandler` will follow symbolic links when handling
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|
requests, this makes it possible for files outside of the specified directory
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|
to be served.
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|
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|
Earlier versions of Python did not scrub control characters from the
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|
log messages emitted to stderr from ``python -m http.server`` or the
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|
default :class:`BaseHTTPRequestHandler` ``.log_message``
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|
implementation. This could allow remote clients connecting to your
|
|
server to send nefarious control codes to your terminal.
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.. versionchanged:: 3.12
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Control characters are scrubbed in stderr logs.
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