To inspect JSON-RPC calls, you can use logging, debugging tools, or network monitoring to capture and analyze requests and responses. Start by enabling logging in your client or server code to record the raw JSON-RPC payloads. For example, in a Node.js application using Express, you might add middleware to log incoming requests and outgoing responses. In Python, you could use the logging module to print JSON-RPC data before sending or after receiving it. This approach provides direct visibility into the structure and content of the calls, helping you verify parameters, method names, and error codes.
Network tools like Wireshark or browser developer tools (e.g., Chrome DevTools) let you inspect traffic at the protocol level. For HTTP-based JSON-RPC, open the browser’s Network tab, trigger a call, and examine the request/response payloads under the relevant entry. Tools like mitmproxy or Fiddler act as proxies to intercept and display traffic between clients and servers, even for non-browser applications. For example, if your JSON-RPC service runs on http://localhost:3000, configure Fiddler to capture traffic on that port and filter for JSON content. This is useful for debugging issues like malformed JSON or incorrect headers without modifying code.
For deeper integration, frameworks like JSON-RPC libraries often include built-in debugging features. In Java, using a library like jsonrpc4j, you can enable debug mode to log calls. In browser environments, wrapping the fetch or XMLHttpRequest methods lets you intercept outgoing requests. Additionally, tools like Postman or Insomnia allow you to manually craft and send JSON-RPC calls for testing. For example, sending a POST request with a body like {"jsonrpc": "2.0", "method": "getUser", "params": {"id": 1}, "id": 1} lets you validate the server’s response structure. Combining these methods ensures you can troubleshoot both client and server-side issues efficiently.