:mod:`http.client` --- HTTP protocol client
===========================================

.. module:: http.client
   :synopsis: HTTP and HTTPS protocol client (requires sockets).


.. index::
   pair: HTTP; protocol
   single: HTTP; http.client (standard module)

.. index:: module: urllib.request

**Source code:** :source:`Lib/http/client.py`

--------------

This module defines classes which implement the client side of the HTTP and
HTTPS protocols.  It is normally not used directly --- the module
:mod:`urllib.request` uses it to handle URLs that use HTTP and HTTPS.

.. note::

   HTTPS support is only available if Python was compiled with SSL support
   (through the :mod:`ssl` module).

The module provides the following classes:


.. class:: HTTPConnection(host, port=None[, timeout], \
                          source_address=None)

   An :class:`HTTPConnection` instance represents one transaction with an HTTP
   server.  It should be instantiated passing it a host and optional port
   number.  If no port number is passed, the port is extracted from the host
   string if it has the form ``host:port``, else the default HTTP port (80) is
   used.  If the optional *timeout* parameter is given, blocking
   operations (like connection attempts) will timeout after that many seconds
   (if it is not given, the global default timeout setting is used).
   The optional *source_address* parameter may be a tuple of a (host, port)
   to use as the source address the HTTP connection is made from.

   For example, the following calls all create instances that connect to the server
   at the same host and port::

      >>> h1 = http.client.HTTPConnection('www.python.org')
      >>> h2 = http.client.HTTPConnection('www.python.org:80')
      >>> h3 = http.client.HTTPConnection('www.python.org', 80)
      >>> h4 = http.client.HTTPConnection('www.python.org', 80, timeout=10)

   .. versionchanged:: 3.2
      *source_address* was added.

   .. versionchanged:: 3.4
      The  *strict* parameter was removed. HTTP 0.9-style "Simple Responses" are
      not longer supported.


.. class:: HTTPSConnection(host, port=None, key_file=None, \
                           cert_file=None[, timeout], \
                           source_address=None, *, context=None, \
                           check_hostname=None)

   A subclass of :class:`HTTPConnection` that uses SSL for communication with
   secure servers.  Default port is ``443``.  If *context* is specified, it
   must be a :class:`ssl.SSLContext` instance describing the various SSL
   options.

   *key_file* and *cert_file* are deprecated, please use
   :meth:`ssl.SSLContext.load_cert_chain` instead, or let
   :func:`ssl.create_default_context` select the system's trusted CA
   certificates for you.

   The recommended way to connect to HTTPS hosts on the Internet is as
   follows::

      context = ssl.create_default_context()
      h = client.HTTPSConnection('www.python.org', 443, context=context)

   Please read :ref:`ssl-security` for more information on best practices.

   .. note::
      If *context* is specified and has a :attr:`~ssl.SSLContext.verify_mode`
      of either :data:`~ssl.CERT_OPTIONAL` or :data:`~ssl.CERT_REQUIRED`, then
      by default *host* is matched against the host name(s) allowed by the
      server's certificate.  If you want to change that behaviour, you can
      explicitly set *check_hostname* to False.

   .. versionchanged:: 3.2
      *source_address*, *context* and *check_hostname* were added.

   .. versionchanged:: 3.2
      This class now supports HTTPS virtual hosts if possible (that is,
      if :data:`ssl.HAS_SNI` is true).

   .. versionchanged:: 3.4
      The *strict* parameter was removed. HTTP 0.9-style "Simple Responses" are
      no longer supported.


.. class:: HTTPResponse(sock, debuglevel=0, method=None, url=None)

   Class whose instances are returned upon successful connection.  Not
   instantiated directly by user.

   .. versionchanged:: 3.4
      The *strict* parameter was removed. HTTP 0.9 style "Simple Responses" are
      no longer supported.


The following exceptions are raised as appropriate:


.. exception:: HTTPException

   The base class of the other exceptions in this module.  It is a subclass of
   :exc:`Exception`.


.. exception:: NotConnected

   A subclass of :exc:`HTTPException`.


.. exception:: InvalidURL

   A subclass of :exc:`HTTPException`, raised if a port is given and is either
   non-numeric or empty.


.. exception:: UnknownProtocol

   A subclass of :exc:`HTTPException`.


.. exception:: UnknownTransferEncoding

   A subclass of :exc:`HTTPException`.


.. exception:: UnimplementedFileMode

   A subclass of :exc:`HTTPException`.


.. exception:: IncompleteRead

   A subclass of :exc:`HTTPException`.


.. exception:: ImproperConnectionState

   A subclass of :exc:`HTTPException`.


.. exception:: CannotSendRequest

   A subclass of :exc:`ImproperConnectionState`.


.. exception:: CannotSendHeader

   A subclass of :exc:`ImproperConnectionState`.


.. exception:: ResponseNotReady

   A subclass of :exc:`ImproperConnectionState`.


.. exception:: BadStatusLine

   A subclass of :exc:`HTTPException`.  Raised if a server responds with a HTTP
   status code that we don't understand.


The constants defined in this module are:

.. data:: HTTP_PORT

   The default port for the HTTP protocol (always ``80``).


.. data:: HTTPS_PORT

   The default port for the HTTPS protocol (always ``443``).

and also the following constants for integer status codes:

+------------------------------------------+---------+-----------------------------------------------------------------------+
| Constant                                 | Value   | Definition                                                            |
+==========================================+=========+=======================================================================+
| :const:`CONTINUE`                        | ``100`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.1.1                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.1.1>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`SWITCHING_PROTOCOLS`             | ``101`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.1.2                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.1.2>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`PROCESSING`                      | ``102`` | WEBDAV, `RFC 2518, Section 10.1                                       |
|                                          |         | <http://www.webdav.org/specs/rfc2518.html#STATUS_102>`_               |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`OK`                              | ``200`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.2.1                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.1>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`CREATED`                         | ``201`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.2.2                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.2>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`ACCEPTED`                        | ``202`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.2.3                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.3>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`NON_AUTHORITATIVE_INFORMATION`   | ``203`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.2.4                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.4>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`NO_CONTENT`                      | ``204`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.2.5                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.5>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`RESET_CONTENT`                   | ``205`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.2.6                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.6>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`PARTIAL_CONTENT`                 | ``206`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.2.7                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.7>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`MULTI_STATUS`                    | ``207`` | WEBDAV `RFC 2518, Section 10.2                                        |
|                                          |         | <http://www.webdav.org/specs/rfc2518.html#STATUS_207>`_               |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`IM_USED`                         | ``226`` | Delta encoding in HTTP,                                               |
|                                          |         | :rfc:`3229`, Section 10.4.1                                           |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`MULTIPLE_CHOICES`                | ``300`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.3.1                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.1>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`MOVED_PERMANENTLY`               | ``301`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.3.2                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.2>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`FOUND`                           | ``302`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.3.3                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.3>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`SEE_OTHER`                       | ``303`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.3.4                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.4>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`NOT_MODIFIED`                    | ``304`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.3.5                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.5>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`USE_PROXY`                       | ``305`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.3.6                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.6>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`TEMPORARY_REDIRECT`              | ``307`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.3.8                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.8>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`BAD_REQUEST`                     | ``400`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.1                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.1>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`UNAUTHORIZED`                    | ``401`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.2                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.2>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`PAYMENT_REQUIRED`                | ``402`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.3                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.3>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`FORBIDDEN`                       | ``403`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.4                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.4>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`NOT_FOUND`                       | ``404`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.5                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.5>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`METHOD_NOT_ALLOWED`              | ``405`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.6                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.6>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`NOT_ACCEPTABLE`                  | ``406`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.7                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.7>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`PROXY_AUTHENTICATION_REQUIRED`   | ``407`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.8                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.8>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`REQUEST_TIMEOUT`                 | ``408`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.9                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.9>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`CONFLICT`                        | ``409`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.10                                                               |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.10>`_ |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`GONE`                            | ``410`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.11                                                               |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.11>`_ |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`LENGTH_REQUIRED`                 | ``411`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.12                                                               |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.12>`_ |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`PRECONDITION_FAILED`             | ``412`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.13                                                               |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.13>`_ |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`REQUEST_ENTITY_TOO_LARGE`        | ``413`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.14                                                               |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.14>`_ |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`REQUEST_URI_TOO_LONG`            | ``414`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.15                                                               |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.15>`_ |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`UNSUPPORTED_MEDIA_TYPE`          | ``415`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.16                                                               |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.16>`_ |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`REQUESTED_RANGE_NOT_SATISFIABLE` | ``416`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.17                                                               |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.17>`_ |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`EXPECTATION_FAILED`              | ``417`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.4.18                                                               |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.18>`_ |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`UNPROCESSABLE_ENTITY`            | ``422`` | WEBDAV, `RFC 2518, Section 10.3                                       |
|                                          |         | <http://www.webdav.org/specs/rfc2518.html#STATUS_422>`_               |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`LOCKED`                          | ``423`` | WEBDAV `RFC 2518, Section 10.4                                        |
|                                          |         | <http://www.webdav.org/specs/rfc2518.html#STATUS_423>`_               |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`FAILED_DEPENDENCY`               | ``424`` | WEBDAV, `RFC 2518, Section 10.5                                       |
|                                          |         | <http://www.webdav.org/specs/rfc2518.html#STATUS_424>`_               |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`UPGRADE_REQUIRED`                | ``426`` | HTTP Upgrade to TLS,                                                  |
|                                          |         | :rfc:`2817`, Section 6                                                |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`PRECONDITION_REQUIRED`           | ``428`` | Additional HTTP Status Codes,                                         |
|                                          |         | :rfc:`6585`, Section 3                                                |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`TOO_MANY_REQUESTS`               | ``429`` | Additional HTTP Status Codes,                                         |
|                                          |         | :rfc:`6585`, Section 4                                                |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`REQUEST_HEADER_FIELDS_TOO_LARGE` | ``431`` | Additional HTTP Status Codes,                                         |
|                                          |         | :rfc:`6585`, Section 5                                                |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`INTERNAL_SERVER_ERROR`           | ``500`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.5.1                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.1>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`NOT_IMPLEMENTED`                 | ``501`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.5.2                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.2>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`BAD_GATEWAY`                     | ``502`` | HTTP/1.1 `RFC 2616, Section                                           |
|                                          |         | 10.5.3                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.3>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`SERVICE_UNAVAILABLE`             | ``503`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.5.4                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.4>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`GATEWAY_TIMEOUT`                 | ``504`` | HTTP/1.1 `RFC 2616, Section                                           |
|                                          |         | 10.5.5                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.5>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`HTTP_VERSION_NOT_SUPPORTED`      | ``505`` | HTTP/1.1, `RFC 2616, Section                                          |
|                                          |         | 10.5.6                                                                |
|                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.6>`_  |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`INSUFFICIENT_STORAGE`            | ``507`` | WEBDAV, `RFC 2518, Section 10.6                                       |
|                                          |         | <http://www.webdav.org/specs/rfc2518.html#STATUS_507>`_               |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`NOT_EXTENDED`                    | ``510`` | An HTTP Extension Framework,                                          |
|                                          |         | :rfc:`2774`, Section 7                                                |
+------------------------------------------+---------+-----------------------------------------------------------------------+
| :const:`NETWORK_AUTHENTICATION_REQUIRED` | ``511`` | Additional HTTP Status Codes,                                         |
|                                          |         | :rfc:`6585`, Section 6                                                |
+------------------------------------------+---------+-----------------------------------------------------------------------+

.. versionchanged:: 3.3
   Added codes ``428``, ``429``, ``431`` and ``511`` from :rfc:`6585`.


.. data:: responses

   This dictionary maps the HTTP 1.1 status codes to the W3C names.

   Example: ``http.client.responses[http.client.NOT_FOUND]`` is ``'Not Found'``.


.. _httpconnection-objects:

HTTPConnection Objects
----------------------

:class:`HTTPConnection` instances have the following methods:


.. method:: HTTPConnection.request(method, url, body=None, headers={})

   This will send a request to the server using the HTTP request
   method *method* and the selector *url*.  If the *body* argument is
   present, it should be string or bytes object of data to send after
   the headers are finished.  Strings are encoded as ISO-8859-1, the
   default charset for HTTP.  To use other encodings, pass a bytes
   object.  The Content-Length header is set to the length of the
   string.

   The *body* may also be an open :term:`file object`, in which case the
   contents of the file is sent; this file object should support ``fileno()``
   and ``read()`` methods. The header Content-Length is automatically set to
   the length of the file as reported by stat. The *body* argument may also be
   an iterable and Content-Length header should be explicitly provided when the
   body is an iterable.

   The *headers* argument should be a mapping of extra HTTP
   headers to send with the request.

   .. versionadded:: 3.2
      *body* can now be an iterable.

.. method:: HTTPConnection.getresponse()

   Should be called after a request is sent to get the response from the server.
   Returns an :class:`HTTPResponse` instance.

   .. note::

      Note that you must have read the whole response before you can send a new
      request to the server.


.. method:: HTTPConnection.set_debuglevel(level)

   Set the debugging level.  The default debug level is ``0``, meaning no
   debugging output is printed.  Any value greater than ``0`` will cause all
   currently defined debug output to be printed to stdout.  The ``debuglevel``
   is passed to any new :class:`HTTPResponse` objects that are created.

   .. versionadded:: 3.1


.. method:: HTTPConnection.set_tunnel(host, port=None, headers=None)

   Set the host and the port for HTTP Connect Tunnelling. This allows running
   the connection through a proxy server.

   The host and port arguments specify the endpoint of the tunneled connection
   (i.e. the address included in the CONNECT request, *not* the address of the
   proxy server).

   The headers argument should be a mapping of extra HTTP headers to send with
   the CONNECT request.

   For example, to tunnel through a HTTPS proxy server running locally on port
   8080, we would pass the address of the proxy to the :class:`HTTPSConnection`
   constructor, and the address of the host that we eventually want to reach to
   the :meth:`~HTTPConnection.set_tunnel` method::

      >>> import http.client
      >>> conn = http.client.HTTPSConnection("localhost", 8080)
      >>> conn.set_tunnel("www.python.org")
      >>> conn.request("HEAD","/index.html")

   .. versionadded:: 3.2


.. method:: HTTPConnection.connect()

   Connect to the server specified when the object was created.


.. method:: HTTPConnection.close()

   Close the connection to the server.

As an alternative to using the :meth:`request` method described above, you can
also send your request step by step, by using the four functions below.


.. method:: HTTPConnection.putrequest(request, selector, skip_host=False, skip_accept_encoding=False)

   This should be the first call after the connection to the server has been made.
   It sends a line to the server consisting of the *request* string, the *selector*
   string, and the HTTP version (``HTTP/1.1``).  To disable automatic sending of
   ``Host:`` or ``Accept-Encoding:`` headers (for example to accept additional
   content encodings), specify *skip_host* or *skip_accept_encoding* with non-False
   values.


.. method:: HTTPConnection.putheader(header, argument[, ...])

   Send an :rfc:`822`\ -style header to the server.  It sends a line to the server
   consisting of the header, a colon and a space, and the first argument.  If more
   arguments are given, continuation lines are sent, each consisting of a tab and
   an argument.


.. method:: HTTPConnection.endheaders(message_body=None)

   Send a blank line to the server, signalling the end of the headers. The
   optional *message_body* argument can be used to pass a message body
   associated with the request.  The message body will be sent in the same
   packet as the message headers if it is string, otherwise it is sent in a
   separate packet.

.. method:: HTTPConnection.send(data)

   Send data to the server.  This should be used directly only after the
   :meth:`endheaders` method has been called and before :meth:`getresponse` is
   called.


.. _httpresponse-objects:

HTTPResponse Objects
--------------------

An :class:`HTTPResponse` instance wraps the HTTP response from the
server.  It provides access to the request headers and the entity
body.  The response is an iterable object and can be used in a with
statement.


.. method:: HTTPResponse.read([amt])

   Reads and returns the response body, or up to the next *amt* bytes.

.. method:: HTTPResponse.readinto(b)

   Reads up to the next len(b) bytes of the response body into the buffer *b*.
   Returns the number of bytes read.

   .. versionadded:: 3.3

.. method:: HTTPResponse.getheader(name, default=None)

   Return the value of the header *name*, or *default* if there is no header
   matching *name*.  If there is more than one  header with the name *name*,
   return all of the values joined by ', '.  If 'default' is any iterable other
   than a single string, its elements are similarly returned joined by commas.


.. method:: HTTPResponse.getheaders()

   Return a list of (header, value) tuples.

.. method:: HTTPResponse.fileno()

   Return the ``fileno`` of the underlying socket.

.. attribute:: HTTPResponse.msg

   A :class:`http.client.HTTPMessage` instance containing the response
   headers.  :class:`http.client.HTTPMessage` is a subclass of
   :class:`email.message.Message`.


.. attribute:: HTTPResponse.version

   HTTP protocol version used by server.  10 for HTTP/1.0, 11 for HTTP/1.1.


.. attribute:: HTTPResponse.status

   Status code returned by server.


.. attribute:: HTTPResponse.reason

   Reason phrase returned by server.


.. attribute:: HTTPResponse.debuglevel

   A debugging hook.  If :attr:`debuglevel` is greater than zero, messages
   will be printed to stdout as the response is read and parsed.

.. attribute:: HTTPResponse.closed

   Is ``True`` if the stream is closed.

Examples
--------

Here is an example session that uses the ``GET`` method::

   >>> import http.client
   >>> conn = http.client.HTTPConnection("www.python.org")
   >>> conn.request("GET", "/index.html")
   >>> r1 = conn.getresponse()
   >>> print(r1.status, r1.reason)
   200 OK
   >>> data1 = r1.read()  # This will return entire content.
   >>> # The following example demonstrates reading data in chunks.
   >>> conn.request("GET", "/index.html")
   >>> r1 = conn.getresponse()
   >>> while not r1.closed:
   ...     print(r1.read(200)) # 200 bytes
   b'<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"...
   ...
   >>> # Example of an invalid request
   >>> conn.request("GET", "/parrot.spam")
   >>> r2 = conn.getresponse()
   >>> print(r2.status, r2.reason)
   404 Not Found
   >>> data2 = r2.read()
   >>> conn.close()

Here is an example session that uses the ``HEAD`` method.  Note that the
``HEAD`` method never returns any data. ::

   >>> import http.client
   >>> conn = http.client.HTTPConnection("www.python.org")
   >>> conn.request("HEAD","/index.html")
   >>> res = conn.getresponse()
   >>> print(res.status, res.reason)
   200 OK
   >>> data = res.read()
   >>> print(len(data))
   0
   >>> data == b''
   True

Here is an example session that shows how to ``POST`` requests::

   >>> import http.client, urllib.parse
   >>> params = urllib.parse.urlencode({'@number': 12524, '@type': 'issue', '@action': 'show'})
   >>> headers = {"Content-type": "application/x-www-form-urlencoded",
   ...            "Accept": "text/plain"}
   >>> conn = http.client.HTTPConnection("bugs.python.org")
   >>> conn.request("POST", "", params, headers)
   >>> response = conn.getresponse()
   >>> print(response.status, response.reason)
   302 Found
   >>> data = response.read()
   >>> data
   b'Redirecting to <a href="http://bugs.python.org/issue12524">http://bugs.python.org/issue12524</a>'
   >>> conn.close()

Client side ``HTTP PUT`` requests are very similar to ``POST`` requests. The
difference lies only the server side where HTTP server will allow resources to
be created via ``PUT`` request. It should be noted that custom HTTP methods
+are also handled in :class:`urllib.request.Request` by sending the appropriate
+method attribute.Here is an example session that shows how to do ``PUT``
request using http.client::

    >>> # This creates an HTTP message
    >>> # with the content of BODY as the enclosed representation
    >>> # for the resource http://localhost:8080/file
    ...
    >>> import http.client
    >>> BODY = "***filecontents***"
    >>> conn = http.client.HTTPConnection("localhost", 8080)
    >>> conn.request("PUT", "/file", BODY)
    >>> response = conn.getresponse()
    >>> print(response.status, response.reason)
    200, OK

.. _httpmessage-objects:

HTTPMessage Objects
-------------------

An :class:`http.client.HTTPMessage` instance holds the headers from an HTTP
response.  It is implemented using the :class:`email.message.Message` class.

.. XXX Define the methods that clients can depend upon between versions.
