XMLRPC server and client modules in Python

XML-RPC (XML Remote Procedure Call) is a protocol that allows programs to make function calls over HTTP using XML for encoding. Python's xmlrpc.server and xmlrpc.client modules make it easy to create cross-platform, language-independent servers and clients.

Creating an XML-RPC Server

We use SimpleXMLRPCServer to create a server instance and register functions that clients can call remotely. The server listens for incoming requests and executes the appropriate functions ?

Example

from xmlrpc.server import SimpleXMLRPCServer
from xmlrpc.server import SimpleXMLRPCRequestHandler

class RequestHandler(SimpleXMLRPCRequestHandler):
    rpc_paths = ('/RPC2',)

with SimpleXMLRPCServer(('localhost', 9000),
                        requestHandler=RequestHandler) as server:
    server.register_introspection_functions()
    
    # Register len() function
    server.register_function(len)
    
    # Register a function under a different name
    @server.register_function(name='rmndr')
    def remainder_function(x, y):
        return x // y
    
    # Register a function under function.__name__
    @server.register_function
    def modl(x, y):
        return x % y
    
    print("Server running on localhost:9000...")
    server.serve_forever()

Key Components

The server setup involves several important components:

• RequestHandler: Defines the RPC path ('/RPC2')
• register_introspection_functions(): Enables system methods like listMethods()
• register_function(): Registers functions with optional custom names
• serve_forever(): Puts server in infinite loop to handle requests

Creating an XML-RPC Client

The client connects to the server using xmlrpc.client.ServerProxy and can call registered functions as if they were local ?

Example

import xmlrpc.client

# Connect to the server
s = xmlrpc.client.ServerProxy('http://localhost:9000')

print(s.len("Tutorialspoint"))
print(s.rmndr(12, 5))
print(s.modl(7, 3))

# Print list of available methods
print(s.system.listMethods())

Output

Running the above client code gives us the following result ?

14
2
1
['len', 'modl', 'rmndr', 'system.listMethods', 'system.methodHelp', 'system.methodSignature']

How It Works

The XML-RPC protocol works by:

1. Client sends HTTP POST request with XML-encoded function call
2. Server receives request, decodes XML, and executes function
3. Server encodes result as XML and sends HTTP response
4. Client receives and decodes the XML response

Conclusion

XML-RPC provides a simple way to create distributed applications in Python. The server registers functions that clients can call remotely over HTTP, making it ideal for cross-platform communication between different programming languages.