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Chapter 18
RPC

This is a directory of program listings from Chapter 18 of the book:

Foundations of Python Network Programming
Third Edition, October 2014
by Brandon Rhodes and John Goerzen

You can learn more about the book by visiting the root of this GitHub source code repository.

These scripts were written for Python 3, but most of them will run under Python 2. Use 3to2 to convert them to the older syntax. The exception is that xmlrpc_client.py runs into trouble because it attempts to send Unicode strings in its RPC call, but the Standard Library xmlrpclib does not know how to encode them.

The chapter explores three kinds of RPC: XML-RPC, JSON-RPC, and a Python-specific system called RPyC. The XML-RPC protocol is supported by the Standard Library, while the other two require third-party packages from the Python Package Index.

In each case, the chapter provides both a small sample server and then a client that puts the server through its paces. As all of the examples are hard-coded to use localhost, they can all be safely run right on your machine.

XML-RPC

$ python3 xmlrpc_server.py &>server.log &

$ python3 xmlrpc_client.py
xÿz
55
[0.0, 8.0]
[-1.0]
[1, 2.0, 'three']
[1, 2.0, 'three']
{'data': {'age': 42, 'sex': 'M'}, 'name': 'Arthur'}
Traceback (most recent call last):
  ...
xmlrpc.client.Fault: <Fault 1: "<class 'ValueError'>:math domain error">

$ python3 xmlrpc_introspect.py
Here are the functions supported by this server:
addtogether(...)
   Add together everything in the list `things`.
quadratic(...)
   Determine `x` values satisfying: `a` * x*x + `b` * x + c == 0
remote_repr(...)
   Return the `repr()` rendering of the supplied `arg`.

$ python3 xmlrpc_multicall.py
abc
[0.0, 8.0]
[1, 2.0, 'three']

$ cat server.log
Server ready
127.0.0.1 - - [25/Mar/2014 19:20:08] "POST /RPC2 HTTP/1.1" 200 -
127.0.0.1 - - [25/Mar/2014 19:20:08] "POST /RPC2 HTTP/1.1" 200 -
...
127.0.0.1 - - [25/Mar/2014 19:20:08] "POST /RPC2 HTTP/1.1" 200 -
127.0.0.1 - - [25/Mar/2014 19:20:08] "POST /RPC2 HTTP/1.1" 200 -

JSON-RPC

$ python3 jsonrpc_server.py &>server.log &

$ python3 jsonrpc_client.py
[[3, [1, 2, 3]], [None, 27], [2, {'Rigel': 0.12, 'Sirius': -1.46}]]

$ cat server.log
Starting server
127.0.0.1 - - [25/Mar/2014 19:20:08] "POST / HTTP/1.1" 200 -

RPyC

$ python3 rpyc_server.py &>server.log &

$ python3 rpyc_client.py
Noisy: 'Simple\n'
Noisy: 'is\n'
Noisy: 'better\n'
Noisy: 'than\n'
Noisy: 'complex.\n'
The number of lines in the file was 5

$ cat server.log
Client has invoked exposed_line_counter()

Consult the chapter to learn about how RPyC is quite different from the other mechanisms. While the other two only support simple function invocation, RPyC is in fact a general two-way object publishing protocol.