537 lines
20 KiB
ReStructuredText
537 lines
20 KiB
ReStructuredText
:mod:`xmlrpc.client` --- XML-RPC client access
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==============================================
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.. module:: xmlrpc.client
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:synopsis: XML-RPC client access.
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.. moduleauthor:: Fredrik Lundh <fredrik@pythonware.com>
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.. sectionauthor:: Eric S. Raymond <esr@snark.thyrsus.com>
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.. XXX Not everything is documented yet. It might be good to describe
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Marshaller, Unmarshaller, getparser, dumps, loads, and Transport.
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**Source code:** :source:`Lib/xmlrpc/client.py`
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--------------
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XML-RPC is a Remote Procedure Call method that uses XML passed via HTTP as a
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transport. With it, a client can call methods with parameters on a remote
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server (the server is named by a URI) and get back structured data. This module
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supports writing XML-RPC client code; it handles all the details of translating
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between conformable Python objects and XML on the wire.
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.. class:: ServerProxy(uri, transport=None, encoding=None, verbose=False, allow_none=False, use_datetime=False)
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A :class:`ServerProxy` instance is an object that manages communication with a
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remote XML-RPC server. The required first argument is a URI (Uniform Resource
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Indicator), and will normally be the URL of the server. The optional second
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argument is a transport factory instance; by default it is an internal
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:class:`SafeTransport` instance for https: URLs and an internal HTTP
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:class:`Transport` instance otherwise. The optional third argument is an
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encoding, by default UTF-8. The optional fourth argument is a debugging flag.
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If *allow_none* is true, the Python constant ``None`` will be translated into
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XML; the default behaviour is for ``None`` to raise a :exc:`TypeError`. This is
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a commonly-used extension to the XML-RPC specification, but isn't supported by
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all clients and servers; see http://ontosys.com/xml-rpc/extensions.php for a
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description. The *use_datetime* flag can be used to cause date/time values to
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be presented as :class:`datetime.datetime` objects; this is false by default.
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:class:`datetime.datetime` objects may be passed to calls.
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Both the HTTP and HTTPS transports support the URL syntax extension for HTTP
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Basic Authentication: ``http://user:pass@host:port/path``. The ``user:pass``
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portion will be base64-encoded as an HTTP 'Authorization' header, and sent to
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the remote server as part of the connection process when invoking an XML-RPC
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method. You only need to use this if the remote server requires a Basic
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Authentication user and password.
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The returned instance is a proxy object with methods that can be used to invoke
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corresponding RPC calls on the remote server. If the remote server supports the
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introspection API, the proxy can also be used to query the remote server for the
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methods it supports (service discovery) and fetch other server-associated
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metadata.
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:class:`ServerProxy` instance methods take Python basic types and objects as
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arguments and return Python basic types and classes. Types that are conformable
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(e.g. that can be marshalled through XML), include the following (and except
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where noted, they are unmarshalled as the same Python type):
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+---------------------------------+---------------------------------------------+
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| Name | Meaning |
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+=================================+=============================================+
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| :const:`boolean` | The :const:`True` and :const:`False` |
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| | constants |
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+---------------------------------+---------------------------------------------+
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| :const:`integers` | Pass in directly |
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+---------------------------------+---------------------------------------------+
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| :const:`floating-point numbers` | Pass in directly |
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+---------------------------------+---------------------------------------------+
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| :const:`strings` | Pass in directly |
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+---------------------------------+---------------------------------------------+
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| :const:`arrays` | Any Python sequence type containing |
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| | conformable elements. Arrays are returned |
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| | as lists |
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+---------------------------------+---------------------------------------------+
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| :const:`structures` | A Python dictionary. Keys must be strings, |
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| | values may be any conformable type. Objects |
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| | of user-defined classes can be passed in; |
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| | only their *__dict__* attribute is |
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| | transmitted. |
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+---------------------------------+---------------------------------------------+
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| :const:`dates` | in seconds since the epoch (pass in an |
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| | instance of the :class:`DateTime` class) or |
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| | a :class:`datetime.datetime` instance. |
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+---------------------------------+---------------------------------------------+
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| :const:`binary data` | pass in an instance of the :class:`Binary` |
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| | wrapper class |
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+---------------------------------+---------------------------------------------+
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This is the full set of data types supported by XML-RPC. Method calls may also
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raise a special :exc:`Fault` instance, used to signal XML-RPC server errors, or
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:exc:`ProtocolError` used to signal an error in the HTTP/HTTPS transport layer.
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Both :exc:`Fault` and :exc:`ProtocolError` derive from a base class called
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:exc:`Error`. Note that the xmlrpc client module currently does not marshal
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instances of subclasses of built-in types.
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When passing strings, characters special to XML such as ``<``, ``>``, and ``&``
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will be automatically escaped. However, it's the caller's responsibility to
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ensure that the string is free of characters that aren't allowed in XML, such as
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the control characters with ASCII values between 0 and 31 (except, of course,
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tab, newline and carriage return); failing to do this will result in an XML-RPC
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request that isn't well-formed XML. If you have to pass arbitrary strings via
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XML-RPC, use the :class:`Binary` wrapper class described below.
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:class:`Server` is retained as an alias for :class:`ServerProxy` for backwards
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compatibility. New code should use :class:`ServerProxy`.
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.. seealso::
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`XML-RPC HOWTO <http://www.tldp.org/HOWTO/XML-RPC-HOWTO/index.html>`_
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A good description of XML-RPC operation and client software in several languages.
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Contains pretty much everything an XML-RPC client developer needs to know.
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`XML-RPC Introspection <http://xmlrpc-c.sourceforge.net/introspection.html>`_
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Describes the XML-RPC protocol extension for introspection.
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`XML-RPC Specification <http://www.xmlrpc.com/spec>`_
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The official specification.
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`Unofficial XML-RPC Errata <http://effbot.org/zone/xmlrpc-errata.htm>`_
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Fredrik Lundh's "unofficial errata, intended to clarify certain
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details in the XML-RPC specification, as well as hint at
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'best practices' to use when designing your own XML-RPC
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implementations."
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.. _serverproxy-objects:
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ServerProxy Objects
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-------------------
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A :class:`ServerProxy` instance has a method corresponding to each remote
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procedure call accepted by the XML-RPC server. Calling the method performs an
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RPC, dispatched by both name and argument signature (e.g. the same method name
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can be overloaded with multiple argument signatures). The RPC finishes by
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returning a value, which may be either returned data in a conformant type or a
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:class:`Fault` or :class:`ProtocolError` object indicating an error.
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Servers that support the XML introspection API support some common methods
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grouped under the reserved :attr:`system` attribute:
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.. method:: ServerProxy.system.listMethods()
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This method returns a list of strings, one for each (non-system) method
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supported by the XML-RPC server.
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.. method:: ServerProxy.system.methodSignature(name)
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This method takes one parameter, the name of a method implemented by the XML-RPC
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server. It returns an array of possible signatures for this method. A signature
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is an array of types. The first of these types is the return type of the method,
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the rest are parameters.
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Because multiple signatures (ie. overloading) is permitted, this method returns
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a list of signatures rather than a singleton.
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Signatures themselves are restricted to the top level parameters expected by a
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method. For instance if a method expects one array of structs as a parameter,
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and it returns a string, its signature is simply "string, array". If it expects
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three integers and returns a string, its signature is "string, int, int, int".
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If no signature is defined for the method, a non-array value is returned. In
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Python this means that the type of the returned value will be something other
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than list.
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.. method:: ServerProxy.system.methodHelp(name)
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This method takes one parameter, the name of a method implemented by the XML-RPC
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server. It returns a documentation string describing the use of that method. If
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no such string is available, an empty string is returned. The documentation
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string may contain HTML markup.
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A working example follows. The server code::
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from xmlrpc.server import SimpleXMLRPCServer
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def is_even(n):
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return n%2 == 0
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server = SimpleXMLRPCServer(("localhost", 8000))
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print("Listening on port 8000...")
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server.register_function(is_even, "is_even")
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server.serve_forever()
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The client code for the preceding server::
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import xmlrpc.client
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proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
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print("3 is even: %s" % str(proxy.is_even(3)))
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print("100 is even: %s" % str(proxy.is_even(100)))
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.. _datetime-objects:
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DateTime Objects
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----------------
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This class may be initialized with seconds since the epoch, a time
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tuple, an ISO 8601 time/date string, or a :class:`datetime.datetime`
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instance. It has the following methods, supported mainly for internal
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use by the marshalling/unmarshalling code:
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.. method:: DateTime.decode(string)
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Accept a string as the instance's new time value.
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.. method:: DateTime.encode(out)
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Write the XML-RPC encoding of this :class:`DateTime` item to the *out* stream
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object.
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It also supports certain of Python's built-in operators through rich comparison
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and :meth:`__repr__` methods.
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A working example follows. The server code::
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import datetime
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from xmlrpc.server import SimpleXMLRPCServer
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import xmlrpc.client
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def today():
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today = datetime.datetime.today()
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return xmlrpc.client.DateTime(today)
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server = SimpleXMLRPCServer(("localhost", 8000))
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print("Listening on port 8000...")
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server.register_function(today, "today")
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server.serve_forever()
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The client code for the preceding server::
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import xmlrpc.client
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import datetime
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proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
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today = proxy.today()
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# convert the ISO8601 string to a datetime object
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converted = datetime.datetime.strptime(today.value, "%Y%m%dT%H:%M:%S")
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print("Today: %s" % converted.strftime("%d.%m.%Y, %H:%M"))
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.. _binary-objects:
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Binary Objects
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--------------
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This class may be initialized from string data (which may include NULs). The
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primary access to the content of a :class:`Binary` object is provided by an
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attribute:
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.. attribute:: Binary.data
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The binary data encapsulated by the :class:`Binary` instance. The data is
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provided as an 8-bit string.
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:class:`Binary` objects have the following methods, supported mainly for
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internal use by the marshalling/unmarshalling code:
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.. method:: Binary.decode(string)
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Accept a base64 string and decode it as the instance's new data.
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.. method:: Binary.encode(out)
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Write the XML-RPC base 64 encoding of this binary item to the out stream object.
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The encoded data will have newlines every 76 characters as per
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`RFC 2045 section 6.8 <http://tools.ietf.org/html/rfc2045#section-6.8>`_,
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which was the de facto standard base64 specification when the
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XML-RPC spec was written.
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It also supports certain of Python's built-in operators through :meth:`__eq__`
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and :meth:`__ne__` methods.
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Example usage of the binary objects. We're going to transfer an image over
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XMLRPC::
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from xmlrpc.server import SimpleXMLRPCServer
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import xmlrpc.client
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def python_logo():
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with open("python_logo.jpg", "rb") as handle:
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return xmlrpc.client.Binary(handle.read())
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server = SimpleXMLRPCServer(("localhost", 8000))
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print("Listening on port 8000...")
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server.register_function(python_logo, 'python_logo')
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server.serve_forever()
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The client gets the image and saves it to a file::
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import xmlrpc.client
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proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
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with open("fetched_python_logo.jpg", "wb") as handle:
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handle.write(proxy.python_logo().data)
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.. _fault-objects:
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Fault Objects
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-------------
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A :class:`Fault` object encapsulates the content of an XML-RPC fault tag. Fault
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objects have the following attributes:
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.. attribute:: Fault.faultCode
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A string indicating the fault type.
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.. attribute:: Fault.faultString
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A string containing a diagnostic message associated with the fault.
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In the following example we're going to intentionally cause a :exc:`Fault` by
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returning a complex type object. The server code::
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from xmlrpc.server import SimpleXMLRPCServer
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# A marshalling error is going to occur because we're returning a
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# complex number
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def add(x,y):
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return x+y+0j
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server = SimpleXMLRPCServer(("localhost", 8000))
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print("Listening on port 8000...")
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server.register_function(add, 'add')
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server.serve_forever()
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The client code for the preceding server::
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import xmlrpc.client
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proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
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try:
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proxy.add(2, 5)
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except xmlrpc.client.Fault as err:
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print("A fault occurred")
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print("Fault code: %d" % err.faultCode)
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print("Fault string: %s" % err.faultString)
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.. _protocol-error-objects:
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ProtocolError Objects
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---------------------
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A :class:`ProtocolError` object describes a protocol error in the underlying
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transport layer (such as a 404 'not found' error if the server named by the URI
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does not exist). It has the following attributes:
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.. attribute:: ProtocolError.url
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The URI or URL that triggered the error.
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.. attribute:: ProtocolError.errcode
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The error code.
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.. attribute:: ProtocolError.errmsg
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The error message or diagnostic string.
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.. attribute:: ProtocolError.headers
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A dict containing the headers of the HTTP/HTTPS request that triggered the
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error.
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In the following example we're going to intentionally cause a :exc:`ProtocolError`
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by providing an invalid URI::
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import xmlrpc.client
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# create a ServerProxy with an URI that doesn't respond to XMLRPC requests
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proxy = xmlrpc.client.ServerProxy("http://google.com/")
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try:
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proxy.some_method()
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except xmlrpc.client.ProtocolError as err:
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print("A protocol error occurred")
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print("URL: %s" % err.url)
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print("HTTP/HTTPS headers: %s" % err.headers)
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print("Error code: %d" % err.errcode)
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print("Error message: %s" % err.errmsg)
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MultiCall Objects
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-----------------
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In http://www.xmlrpc.com/discuss/msgReader%241208, an approach is presented to
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encapsulate multiple calls to a remote server into a single request.
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.. class:: MultiCall(server)
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Create an object used to boxcar method calls. *server* is the eventual target of
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the call. Calls can be made to the result object, but they will immediately
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return ``None``, and only store the call name and parameters in the
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:class:`MultiCall` object. Calling the object itself causes all stored calls to
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be transmitted as a single ``system.multicall`` request. The result of this call
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is a :term:`generator`; iterating over this generator yields the individual
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results.
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A usage example of this class follows. The server code ::
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from xmlrpc.server import SimpleXMLRPCServer
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def add(x,y):
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return x+y
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def subtract(x, y):
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return x-y
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def multiply(x, y):
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return x*y
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def divide(x, y):
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return x/y
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# A simple server with simple arithmetic functions
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server = SimpleXMLRPCServer(("localhost", 8000))
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print("Listening on port 8000...")
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server.register_multicall_functions()
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server.register_function(add, 'add')
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server.register_function(subtract, 'subtract')
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server.register_function(multiply, 'multiply')
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server.register_function(divide, 'divide')
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server.serve_forever()
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The client code for the preceding server::
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import xmlrpc.client
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proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
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multicall = xmlrpc.client.MultiCall(proxy)
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multicall.add(7,3)
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multicall.subtract(7,3)
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multicall.multiply(7,3)
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multicall.divide(7,3)
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result = multicall()
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print("7+3=%d, 7-3=%d, 7*3=%d, 7/3=%d" % tuple(result))
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Convenience Functions
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---------------------
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.. function:: dumps(params, methodname=None, methodresponse=None, encoding=None, allow_none=False)
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Convert *params* into an XML-RPC request. or into a response if *methodresponse*
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is true. *params* can be either a tuple of arguments or an instance of the
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:exc:`Fault` exception class. If *methodresponse* is true, only a single value
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can be returned, meaning that *params* must be of length 1. *encoding*, if
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supplied, is the encoding to use in the generated XML; the default is UTF-8.
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Python's :const:`None` value cannot be used in standard XML-RPC; to allow using
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it via an extension, provide a true value for *allow_none*.
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.. function:: loads(data, use_datetime=False)
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Convert an XML-RPC request or response into Python objects, a ``(params,
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methodname)``. *params* is a tuple of argument; *methodname* is a string, or
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``None`` if no method name is present in the packet. If the XML-RPC packet
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represents a fault condition, this function will raise a :exc:`Fault` exception.
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The *use_datetime* flag can be used to cause date/time values to be presented as
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:class:`datetime.datetime` objects; this is false by default.
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.. _xmlrpc-client-example:
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Example of Client Usage
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-----------------------
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::
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# simple test program (from the XML-RPC specification)
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from xmlrpc.client import ServerProxy, Error
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# server = ServerProxy("http://localhost:8000") # local server
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server = ServerProxy("http://betty.userland.com")
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print(server)
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try:
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print(server.examples.getStateName(41))
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except Error as v:
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print("ERROR", v)
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To access an XML-RPC server through a proxy, you need to define a custom
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transport. The following example shows how:
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.. Example taken from http://lowlife.jp/nobonobo/wiki/xmlrpcwithproxy.html
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::
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import xmlrpc.client, http.client
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class ProxiedTransport(xmlrpc.client.Transport):
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def set_proxy(self, proxy):
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self.proxy = proxy
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def make_connection(self, host):
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self.realhost = host
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h = http.client.HTTP(self.proxy)
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return h
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def send_request(self, connection, handler, request_body):
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connection.putrequest("POST", 'http://%s%s' % (self.realhost, handler))
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def send_host(self, connection, host):
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connection.putheader('Host', self.realhost)
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p = ProxiedTransport()
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p.set_proxy('proxy-server:8080')
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server = xmlrpc.client.Server('http://time.xmlrpc.com/RPC2', transport=p)
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print(server.currentTime.getCurrentTime())
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Example of Client and Server Usage
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----------------------------------
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See :ref:`simplexmlrpcserver-example`.
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