RPC (JSON-RPC, XML-RPC)

RPC (Remote Procedure Call) is a communication method where a program calls a procedure (function) on a remote system as if it were local. The client sends a request to the server, which executes the procedure and returns a response.

RPC abstracts away the details of network communication, making remote calls look like local function calls.

Types of RPC

XML-RPC:

• Uses XML to encode requests and responses.
• Typically sent over HTTP.

Example request:

<?xml version="1.0"?><methodCall>  <methodName>getUser</methodName>  <params>    <param><value><int>123</int></value></param>  </params></methodCall>

Example response:

<?xml version="1.0"?><methodResponse>  <params>    <param>      <value>        <struct>          <member><name>id</name><value><int>123</int></value></member>          <member><name>name</name><value><string>Alice</string></value></member>        </struct>      </value>    </param>  </params></methodResponse>

SON-RPC

• Uses JSON for request/response.
• Lightweight and easier to parse than XML.

Example request:

{  "jsonrpc": "2.0",  "method": "getUser",  "params": { "id": 123 },  "id": 1}

Example response:

{  "jsonrpc": "2.0",  "result": { "id": 123, "name": "Alice" },  "id": 1}

Key Features

• Method-centric → Call a function/method rather than accessing a resource.
• Synchronous → Client waits for server response (though async variants exist).
• Transport agnostic → Usually HTTP, but can use TCP or other protocols.
• Lightweight (JSON-RPC) vs Verbose (XML-RPC).

Advantages

• Simple model — “call a function remotely.”
• Easy to implement for small services.
• JSON-RPC is lightweight, readable, and fast for modern web apps.

Disadvantages

• Less standardised than SOAP or REST.
• Error handling can be inconsistent.
• Not ideal for complex enterprise workflows.
• Limited tooling and ecosystem compared to REST/GraphQL/gRPC.

Use Cases

• Internal services where simplicity is enough.
• Lightweight web services for data retrieval or small operations.
• Legacy systems using XML-RPC.
• Modern microservices or WebSocket-based services can use JSON-RPC