:mod:`!xmlrpc.client` --- XML-RPC client access
.. module:: xmlrpc.client :synopsis: XML-RPC client access.
.. moduleauthor:: Fredrik Lundh <[email protected]>
.. sectionauthor:: Eric S. Raymond <[email protected]>
Source code: :source:`Lib/xmlrpc/client.py`
XML-RPC is a Remote Procedure Call method that uses XML passed via HTTP(S) as a transport. With it, a client can call methods with parameters on a remote server (the server is named by a URI) and get back structured data. This module supports writing XML-RPC client code; it handles all the details of translating between conformable Python objects and XML on the wire.
Warning
The :mod:`xmlrpc.client` module is not secure against maliciously constructed data. If you need to parse untrusted or unauthenticated data see :ref:`xml-vulnerabilities`.
.. versionchanged:: 3.5 For HTTPS URIs, :mod:`xmlrpc.client` now performs all the necessary certificate and hostname checks by default.
.. seealso:: `XML-RPC HOWTO <https://tldp.org/HOWTO/XML-RPC-HOWTO/index.html>`_ A good description of XML-RPC operation and client software in several languages. Contains pretty much everything an XML-RPC client developer needs to know. `XML-RPC Introspection <https://xmlrpc-c.sourceforge.io/introspection.html>`_ Describes the XML-RPC protocol extension for introspection. `XML-RPC Specification <http://xmlrpc.scripting.com/spec.html>`_ The official specification.
A :class:`ServerProxy` instance has a method corresponding to each remote procedure call accepted by the XML-RPC server. Calling the method performs an RPC, dispatched by both name and argument signature (e.g. the same method name can be overloaded with multiple argument signatures). The RPC finishes by returning a value, which may be either returned data in a conformant type or a :class:`Fault` or :class:`ProtocolError` object indicating an error.
Servers that support the XML introspection API support some common methods grouped under the reserved :attr:`~ServerProxy.system` attribute:
.. method:: ServerProxy.system.listMethods() This method returns a list of strings, one for each (non-system) method supported by the XML-RPC server.
.. method:: ServerProxy.system.methodSignature(name) This method takes one parameter, the name of a method implemented by the XML-RPC server. It returns an array of possible signatures for this method. A signature is an array of types. The first of these types is the return type of the method, the rest are parameters. Because multiple signatures (ie. overloading) is permitted, this method returns a list of signatures rather than a singleton. Signatures themselves are restricted to the top level parameters expected by a method. For instance if a method expects one array of structs as a parameter, and it returns a string, its signature is simply "string, array". If it expects three integers and returns a string, its signature is "string, int, int, int". If no signature is defined for the method, a non-array value is returned. In Python this means that the type of the returned value will be something other than list.
.. method:: ServerProxy.system.methodHelp(name) This method takes one parameter, the name of a method implemented by the XML-RPC server. It returns a documentation string describing the use of that method. If no such string is available, an empty string is returned. The documentation string may contain HTML markup.
.. versionchanged:: 3.5 Instances of :class:`ServerProxy` support the :term:`context manager` protocol for closing the underlying transport.
A working example follows. The server code:
from xmlrpc.server import SimpleXMLRPCServer def is_even(n): return n % 2 == 0 server = SimpleXMLRPCServer(("localhost", 8000)) print("Listening on port 8000...") server.register_function(is_even, "is_even") server.serve_forever()
The client code for the preceding server:
import xmlrpc.client with xmlrpc.client.ServerProxy("http://localhost:8000/") as proxy: print("3 is even: %s" % str(proxy.is_even(3))) print("100 is even: %s" % str(proxy.is_even(100)))
This class may be initialized with seconds since the epoch, a time tuple, an ISO 8601 time/date string, or a :class:`datetime.datetime` instance. It has the following methods, supported mainly for internal use by the marshalling/unmarshalling code:
.. method:: decode(string) Accept a string as the instance's new time value.
.. method:: encode(out) Write the XML-RPC encoding of this :class:`DateTime` item to the *out* stream object.
It also supports certain of Python's built-in operators through :meth:`rich comparison <object.__lt__>` and :meth:`~object.__repr__` methods.
A working example follows. The server code:
import datetime from xmlrpc.server import SimpleXMLRPCServer import xmlrpc.client def today(): today = datetime.datetime.today() return xmlrpc.client.DateTime(today) server = SimpleXMLRPCServer(("localhost", 8000)) print("Listening on port 8000...") server.register_function(today, "today") server.serve_forever()
The client code for the preceding server:
import xmlrpc.client import datetime proxy = xmlrpc.client.ServerProxy("http://localhost:8000/") today = proxy.today() # convert the ISO8601 string to a datetime object converted = datetime.datetime.strptime(today.value, "%Y%m%dT%H:%M:%S") print("Today: %s" % converted.strftime("%d.%m.%Y, %H:%M"))
This class may be initialized from bytes data (which may include NULs). The primary access to the content of a :class:`Binary` object is provided by an attribute:
.. attribute:: data The binary data encapsulated by the :class:`Binary` instance. The data is provided as a :class:`bytes` object.
:class:`Binary` objects have the following methods, supported mainly for internal use by the marshalling/unmarshalling code:
.. method:: decode(bytes) Accept a base64 :class:`bytes` object and decode it as the instance's new data.
.. method:: encode(out) Write the XML-RPC base 64 encoding of this binary item to the *out* stream object. The encoded data will have newlines every 76 characters as per :rfc:`RFC 2045 section 6.8 <2045#section-6.8>`, which was the de facto standard base64 specification when the XML-RPC spec was written.
It also supports certain of Python's built-in operators through :meth:`~object.__eq__` and :meth:`~object.__ne__` methods.
Example usage of the binary objects. We're going to transfer an image over XMLRPC:
from xmlrpc.server import SimpleXMLRPCServer import xmlrpc.client def python_logo(): with open("python_logo.jpg", "rb") as handle: return xmlrpc.client.Binary(handle.read()) server = SimpleXMLRPCServer(("localhost", 8000)) print("Listening on port 8000...") server.register_function(python_logo, 'python_logo') server.serve_forever()
The client gets the image and saves it to a file:
import xmlrpc.client proxy = xmlrpc.client.ServerProxy("http://localhost:8000/") with open("fetched_python_logo.jpg", "wb") as handle: handle.write(proxy.python_logo().data)
A :class:`Fault` object encapsulates the content of an XML-RPC fault tag. Fault objects have the following attributes:
.. attribute:: faultCode An int indicating the fault type.
.. attribute:: faultString A string containing a diagnostic message associated with the fault.
In the following example we're going to intentionally cause a :exc:`Fault` by returning a complex type object. The server code:
from xmlrpc.server import SimpleXMLRPCServer # A marshalling error is going to occur because we're returning a # complex number def add(x, y): return x+y+0j server = SimpleXMLRPCServer(("localhost", 8000)) print("Listening on port 8000...") server.register_function(add, 'add') server.serve_forever()
The client code for the preceding server:
import xmlrpc.client proxy = xmlrpc.client.ServerProxy("http://localhost:8000/") try: proxy.add(2, 5) except xmlrpc.client.Fault as err: print("A fault occurred") print("Fault code: %d" % err.faultCode) print("Fault string: %s" % err.faultString)
A :class:`ProtocolError` object describes a protocol error in the underlying transport layer (such as a 404 'not found' error if the server named by the URI does not exist). It has the following attributes:
.. attribute:: url The URI or URL that triggered the error.
.. attribute:: errcode The error code.
.. attribute:: errmsg The error message or diagnostic string.
.. attribute:: headers A dict containing the headers of the HTTP/HTTPS request that triggered the error.
In the following example we're going to intentionally cause a :exc:`ProtocolError` by providing an invalid URI:
import xmlrpc.client # create a ServerProxy with a URI that doesn't respond to XMLRPC requests proxy = xmlrpc.client.ServerProxy("http://google.com/") try: proxy.some_method() except xmlrpc.client.ProtocolError as err: print("A protocol error occurred") print("URL: %s" % err.url) print("HTTP/HTTPS headers: %s" % err.headers) print("Error code: %d" % err.errcode) print("Error message: %s" % err.errmsg)
The :class:`MultiCall` object provides a way to encapsulate multiple calls to a remote server into a single request [1].
Create an object used to boxcar method calls. server is the eventual target of
the call. Calls can be made to the result object, but they will immediately
return None
, and only store the call name and parameters in the
:class:`MultiCall` object. Calling the object itself causes all stored calls to
be transmitted as a single system.multicall
request. The result of this call
is a :term:`generator`; iterating over this generator yields the individual
results.
A usage example of this class follows. The server code:
from xmlrpc.server import SimpleXMLRPCServer def add(x, y): return x + y def subtract(x, y): return x - y def multiply(x, y): return x * y def divide(x, y): return x // y # A simple server with simple arithmetic functions server = SimpleXMLRPCServer(("localhost", 8000)) print("Listening on port 8000...") server.register_multicall_functions() server.register_function(add, 'add') server.register_function(subtract, 'subtract') server.register_function(multiply, 'multiply') server.register_function(divide, 'divide') server.serve_forever()
The client code for the preceding server:
import xmlrpc.client proxy = xmlrpc.client.ServerProxy("http://localhost:8000/") multicall = xmlrpc.client.MultiCall(proxy) multicall.add(7, 3) multicall.subtract(7, 3) multicall.multiply(7, 3) multicall.divide(7, 3) result = multicall() print("7+3=%d, 7-3=%d, 7*3=%d, 7//3=%d" % tuple(result))
.. function:: dumps(params, methodname=None, methodresponse=None, encoding=None, allow_none=False) Convert *params* into an XML-RPC request. or into a response if *methodresponse* is true. *params* can be either a tuple of arguments or an instance of the :exc:`Fault` exception class. If *methodresponse* is true, only a single value can be returned, meaning that *params* must be of length 1. *encoding*, if supplied, is the encoding to use in the generated XML; the default is UTF-8. Python's :const:`None` value cannot be used in standard XML-RPC; to allow using it via an extension, provide a true value for *allow_none*.
.. function:: loads(data, use_datetime=False, use_builtin_types=False) Convert an XML-RPC request or response into Python objects, a ``(params, methodname)``. *params* is a tuple of argument; *methodname* is a string, or ``None`` if no method name is present in the packet. If the XML-RPC packet represents a fault condition, this function will raise a :exc:`Fault` exception. The *use_builtin_types* flag can be used to cause date/time values to be presented as :class:`datetime.datetime` objects and binary data to be presented as :class:`bytes` objects; this flag is false by default. The obsolete *use_datetime* flag is similar to *use_builtin_types* but it applies only to date/time values. .. versionchanged:: 3.3 The *use_builtin_types* flag was added.
# simple test program (from the XML-RPC specification) from xmlrpc.client import ServerProxy, Error # server = ServerProxy("http://localhost:8000") # local server with ServerProxy("http://betty.userland.com") as proxy: print(proxy) try: print(proxy.examples.getStateName(41)) except Error as v: print("ERROR", v)
To access an XML-RPC server through a HTTP proxy, you need to define a custom transport. The following example shows how:
import http.client import xmlrpc.client class ProxiedTransport(xmlrpc.client.Transport): def set_proxy(self, host, port=None, headers=None): self.proxy = host, port self.proxy_headers = headers def make_connection(self, host): connection = http.client.HTTPConnection(*self.proxy) connection.set_tunnel(host, headers=self.proxy_headers) self._connection = host, connection return connection transport = ProxiedTransport() transport.set_proxy('proxy-server', 8080) server = xmlrpc.client.ServerProxy('http://betty.userland.com', transport=transport) print(server.examples.getStateName(41))
See :ref:`simplexmlrpcserver-example`.
Footnotes
[1] | This approach has been first presented in a discussion on xmlrpc.com. |