This project is an implementation of the JSON-RPC v2.0 specification (backwards-compatible) as a client library, for Python 2.7 and Python 3. This version is a fork of jsonrpclib by Josh Marshall, made to be also usable with Pelix/iPOPO remote services.

json, json-rpc, jsonrpclib, jsonrpclib-pelix, python, python3
pip install jsonrpclib-pelix==


JSONRPClib (patched for Pelix and Python 3)

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This library is an implementation of the JSON-RPC specification. It supports both the original 1.0 specification, as well as the new (proposed) 2.0 specification, which includes batch submission, keyword arguments, etc.

This library is licensed under the terms of the Apache Software License 2.0.

About this version

This is a patched version of the original jsonrpclib project by Josh Marshall, available at joshmarshall/jsonrpclib.

The suffix -pelix only indicates that this version works with Pelix Remote Services, but it is not a Pelix specific implementation.

  • This version adds support for Python 3, staying compatible with Python 2.7. The support for Python 2.6 has been dropped, as it was becoming to hard to maintain.
  • It is now possible to use the dispatch_method argument while extending the SimpleJSONRPCDispatcher, to use a custom dispatcher. This allows to use this package by Pelix Remote Services.
  • It can use thread pools to control the number of threads spawned to handle notification requests and clients connections.
  • The modifications added in other forks of this project have been added:
    • From drdaeman/jsonrpclib:
      • Improved JSON-RPC 1.0 support
      • Less strict error response handling
    • From tuomassalo/jsonrpclib:
      • In case of a non-predefined error, raise an AppError and give access to error.data
    • From dejw/jsonrpclib:
      • Custom headers can be sent with request and associated tests
  • Since version 0.4, this package added back the support of Unix sockets.
  • This package cannot be installed with the original jsonrpclib, as it uses the same name.


This library implements the JSON-RPC 2.0 proposed specification in pure Python. It is designed to be as compatible with the syntax of xmlrpclib as possible (it extends where possible), so that projects using xmlrpclib could easily be modified to use JSON and experiment with the differences.

It is backwards-compatible with the 1.0 specification, and supports all of the new proposed features of 2.0, including:

  • Batch submission (via the MultiCall class)
  • Keyword arguments
  • Notifications (both in a batch and 'normal')
  • Class translation using the __jsonclass__ key.

A SimpleJSONRPCServer class has been added. It is intended to emulate the SimpleXMLRPCServer from the default Python distribution.


This library supports ujson, cjson and simplejson, and looks for the parsers in that order (searching first for ujson, cjson, simplejson and finally for the built-in json). One of these must be installed to use this library, although if you have a standard distribution of 2.7+, you should already have one. Keep in mind that ujson is supposed to be the quickest, I believe, so if you are going for full-on optimization you may want to pick it up.


You can install this from PyPI with one of the following commands (sudo might be required):

# Global installation
pip install jsonrpclib-pelix

# Local installation
pip install --user jsonrpclib-pelix

Alternatively, you can download the source from the GitHub repository at tcalmant/jsonrpclib and manually install it with the following commands:

git clone git://github.com/tcalmant/jsonrpclib.git
cd jsonrpclib
python setup.py install

A note on logging

jsonrpclib-pelix uses the logging module from the standard Python library to trace warnings and errors, but doesn't set it up. As a result, you have to configure the Python logging to print out traces.

The easiest way to do it is to add those lines at the beginning of your code:

import logging

More information can be found in the logging documentation page.


This is identical in usage (or should be) to the SimpleXMLRPCServer in the Python standard library. Some of the differences in features are that it obviously supports notification, batch calls, class translation (if left on), etc.

Note: The import line is slightly different from the regular SimpleXMLRPCServer, since the SimpleJSONRPCServer is provided by th jsonrpclib library.

from jsonrpclib.SimpleJSONRPCServer import SimpleJSONRPCServer

server = SimpleJSONRPCServer(('localhost', 8080))
server.register_function(lambda x,y: x+y, 'add')
server.register_function(lambda x: x, 'ping')

To start protect the server with SSL, use the following snippet:

from jsonrpclib.SimpleJSONRPCServer import SimpleJSONRPCServer
import ssl

# Setup the SSL socket
server = SimpleJSONRPCServer(('localhost', 8080), bind_and_activate=False)
server.socket = ssl.wrap_socket(server.socket, certfile='server.pem',

# ... register functions
# Start the server

Notification Thread Pool

By default, notification calls are handled in the request handling thread. It is possible to use a thread pool to handle them, by giving it to the server using the set_notification_pool() method:

from jsonrpclib.SimpleJSONRPCServer import SimpleJSONRPCServer
from jsonrpclib.threadpool import ThreadPool

# Setup the thread pool: between 0 and 10 threads
pool = ThreadPool(max_threads=10, min_threads=0)

# Don't forget to start it

# Setup the server
server = SimpleJSONRPCServer(('localhost', 8080))

# Register methods
server.register_function(lambda x,y: x+y, 'add')
server.register_function(lambda x: x, 'ping')

    # Stop the thread pool (let threads finish their current task)

Threaded server

It is also possible to use a thread pool to handle clients requests, using the PooledJSONRPCServer class. By default, this class uses pool of 0 to 30 threads. A custom pool can be given with the thread_pool parameter of the class constructor.

The notification pool and the request pool are different: by default, a server with a request pool doesn't have a notification pool.

from jsonrpclib.SimpleJSONRPCServer import PooledJSONRPCServer
from jsonrpclib.threadpool import ThreadPool

# Setup the notification and request pools
nofif_pool = ThreadPool(max_threads=10, min_threads=0)
request_pool = ThreadPool(max_threads=50, min_threads=10)

# Don't forget to start them

# Setup the server
server = PooledJSONRPCServer(('localhost', 8080), thread_pool=request_pool)

# Register methods
server.register_function(lambda x,y: x+y, 'add')
server.register_function(lambda x: x, 'ping')

    # Stop the thread pools (let threads finish their current task)

Unix socket

To start a server listening on a Unix socket, you will have to use the following snippet:

from jsonrpclib.SimpleJSONRPCServer import SimpleJSONRPCServer
import os
import socket

# Set the path to the socket file
socket_name = "/tmp/my_socket.socket"

# Ensure that the file doesn't exist yet (or an error will be raised)
if os.path.exists(socket_name):

   # Start the server, indicating the socket family
   # The server will force some flags when in Unix socket mode
   # (no log request, no reuse address, ...)
   srv = SimpleJSONRPCServer(socket_name, address_family=socket.AF_UNIX)

   # ... register methods to the server
   # Run the server
except KeyboardInterrupt:
   # Shutdown the server gracefully
   # You should clean up after the server stopped

This feature is tested on Linux during Travis-CI builds. It also has been tested on Windows Subsystem for Linux (WSL) on Windows 10 1809.

This feature is not available on "pure" Windows, as it doesn't provide the AF_UNIX address family.

Client Usage

This is (obviously) taken from a console session.

>>> import jsonrpclib
>>> server = jsonrpclib.ServerProxy('http://localhost:8080')
>>> server.add(5,6)
>>> server.add(x=5, y=10)
>>> server._notify.add(5,6)
# No result returned...
>>> batch = jsonrpclib.MultiCall(server)
>>> batch.add(5, 6)
>>> batch.ping({'key':'value'})
>>> batch._notify.add(4, 30)
>>> results = batch()
>>> for result in results:
>>> ... print(result)
{'key': 'value'}
# Note that there are only two responses -- this is according to spec.

# Clean up
>>> server('close')()

# Using client history
>>> history = jsonrpclib.history.History()
>>> server = jsonrpclib.ServerProxy('http://localhost:8080', history=history)
>>> server.add(5,6)
>>> print(history.request)
{"id": "f682b956-c8e1-4506-9db4-29fe8bc9fcaa", "jsonrpc": "2.0",
 "method": "add", "params": [5, 6]}
>>> print(history.response)
{"id": "f682b956-c8e1-4506-9db4-29fe8bc9fcaa", "jsonrpc": "2.0",
 "result": 11}

# Clean up
>>> server('close')()

If you need 1.0 functionality, there are a bunch of places you can pass that in, although the best is just to give a specific configuration to jsonrpclib.ServerProxy:

>>> import jsonrpclib
>>> jsonrpclib.config.DEFAULT.version
>>> config = jsonrpclib.config.Config(version=1.0)
>>> history = jsonrpclib.history.History()
>>> server = jsonrpclib.ServerProxy('http://localhost:8080', config=config,
>>> server.add(7, 10)
>>> print(history.request)
{"id": "827b2923-5b37-49a5-8b36-e73920a16d32",
 "method": "add", "params": [7, 10]}
>>> print(history.response)
{"id": "827b2923-5b37-49a5-8b36-e73920a16d32", "error": null, "result": 17}
>>> server('close')()

The equivalent loads and dumps functions also exist, although with minor modifications. The dumps arguments are almost identical, but it adds three arguments: rpcid for the id key, version to specify the JSON-RPC compatibility, and notify if it's a request that you want to be a notification.

Additionally, the loads method does not return the params and method like xmlrpclib, but instead a.) parses for errors, raising ProtocolErrors, and b.) returns the entire structure of the request / response for manual parsing.

Unix sockets

To connect a JSON-RPC server over a Unix socket, you have to use a specific protocol: unix+http.

When connecting to a Unix socket in the current working directory, you can use the following syntax: unix+http://my.socket

When you need to give an absolute path you must use the path part of the URL, the host part will be ignored. For example, you can use this URL to indicate a Unix socket in /var/lib/daemon.socket: unix+http://./var/lib/daemon.socket

Note: Currently, only HTTP is supported over a Unix socket. If you want HTTPS support to be implemented, please create an issue on GitHub

Additional headers

If your remote service requires custom headers in request, you can pass them using the headers keyword argument, when creating the ServerProxy:

>>> import jsonrpclib
>>> server = jsonrpclib.ServerProxy("http://localhost:8080",
                                    headers={'X-Test' : 'Test'})

You can also put additional request headers only for certain method invocation:

>>> import jsonrpclib
>>> server = jsonrpclib.Server("http://localhost:8080")
>>> with server._additional_headers({'X-Test' : 'Test'}) as test_server:
...     test_server.ping(42)
>>> # X-Test header will be no longer sent in requests

Of course _additional_headers contexts can be nested as well.

Class Translation

The library supports an "automatic" class translation process, although it is turned off by default. This can be devastatingly slow if improperly used, so the following is just a short list of things to keep in mind when using it.

  • Keep It (the object) Simple Stupid. (for exceptions, keep reading)
  • Do not require init params (for exceptions, keep reading)
  • Getter properties without setters could be dangerous (read: not tested)

If any of the above are issues, use the _serialize method (see usage below). The server and client must BOTH have the use_jsonclass configuration item on and they must both have access to the same libraries used by the objects for this to work.

If you have excessively nested arguments, it would be better to turn off the translation and manually invoke it on specific objects using jsonrpclib.jsonclass.dump / jsonrpclib.jsonclass.load (since the default behavior recursively goes through attributes and lists/dicts/tuples).

  • Sample file: test_obj.py
# This object is /very/ simple, and the system will look through the
# attributes and serialize what it can.
class TestObj(object):
    foo = 'bar'

# This object requires __init__ params, so it uses the _serialize method
# and returns a tuple of init params and attribute values (the init params
# can be a dict or a list, but the attribute values must be a dict.)
class TestSerial(object):
    foo = 'bar'
    def __init__(self, *args):
        self.args = args
    def _serialize(self):
        return (self.args, {'foo':self.foo,})
  • Sample usage:
>>> import jsonrpclib
>>> import test_obj

# History is used only to print the serialized form of beans
>>> history = jsonrpclib.history.History()
>>> testobj1 = test_obj.TestObj()
>>> testobj2 = test_obj.TestSerial()
>>> server = jsonrpclib.Server('http://localhost:8080', history=history)

# The 'ping' just returns whatever is sent
>>> ping1 = server.ping(testobj1)
>>> ping2 = server.ping(testobj2)

>>> print(history.request)
{"id": "7805f1f9-9abd-49c6-81dc-dbd47229fe13", "jsonrpc": "2.0",
 "method": "ping", "params": [{"__jsonclass__":
                               ["test_obj.TestSerial", []], "foo": "bar"}
>>> print(history.response)
{"id": "7805f1f9-9abd-49c6-81dc-dbd47229fe13", "jsonrpc": "2.0",
 "result": {"__jsonclass__": ["test_obj.TestSerial", []], "foo": "bar"}}

This behavior is turned on by default. To deactivate it, just set the use_jsonclass member of a server Config to False. If you want to use a per-class serialization method, set its name in the serialize_method member of a server Config. Finally, if you are using classes that you have defined in the implementation (as in, not a separate library), you'll need to add those (on BOTH the server and the client) using the config.classes.add() method.

Feedback on this "feature" is very, VERY much appreciated.


Tests are an almost-verbatim drop from the JSON-RPC specification 2.0 page. They can be run using unittest or nosetest:

python -m unittest discover tests
python3 -m unittest discover tests
nosetests tests


In my opinion, there are several reasons to choose JSON over XML for RPC:

  • Much simpler to read (I suppose this is opinion, but I know I'm right. :)
  • Size / Bandwidth - Main reason, a JSON object representation is just much smaller.
  • Parsing - JSON should be much quicker to parse than XML.
  • Easy class passing with jsonclass (when enabled)

In the interest of being fair, there are also a few reasons to choose XML over JSON:

  • Your server doesn't do JSON (rather obvious)
  • Wider XML-RPC support across APIs (can we change this? :))
  • Libraries are more established, i.e. more stable (Let's change this too)