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--- tanszek:oktatas:iss_t:json-rpc [2026/03/01 17:02] – [1. Introduction] knehez
+++ tanszek:oktatas:iss_t:json-rpc [2026/03/01 17:27] (current) – [JSON-RPC Client (Python)] knehez
@@ Line 1: / Line 1: @@
 ===== JSON-RPC =====
-==== 1. Introduction ====
 JSON-RPC (JavaScript Object Notation – Remote Procedure Call) is a lightweight remote procedure call protocol that uses JSON for encoding messages. It allows a client to call functions (methods) on a remote server as if they were local functions.
@@ Line 22: / Line 20: @@
 The current widely used version is JSON-RPC 2.0. https://www.jsonrpc.org/specification
+==== JSON-RPC 2.0 Message Structure ====
+A JSON-RPC request is a JSON object with the following fields:
+  * **jsonrpc** – must be "2.0"
+  * **method** – name of the remote method
+  * **params** – parameters (optional)
+  * **id** – request identifier (used to match response)
+Example request:
+<code json> { "jsonrpc": "2.0", "method": "add", "params": [5, 7], "id": 1 } </code>
+Successful response:
+<code json> { "jsonrpc": "2.0", "result": 12, "id": 1 } </code>
+Error response:
+<code json> { "jsonrpc": "2.0", "error": { "code": -32601, "message": "Method not found" }, "id": 1 } </code>
+==== Notifications ====
+If the client sends a request without an id, it becomes a notification.
+The server must NOT send a response.
+Example:
+<code json> { "jsonrpc": "2.0", "method": "logEvent", "params": {"event": "started"} } </code>
+==== Batch Requests ====
+JSON-RPC supports sending multiple requests in one array:
+<code json> [ {"jsonrpc": "2.0", "method": "add", "params": [1,2], "id": 1}, {"jsonrpc": "2.0", "method": "subtract", "params": [5,3], "id": 2} ] </code>
+==== 6. Practical Example in Python ====
+In this section, we implement a simple JSON-RPC server and client using Python.
+We will use:
+  * Flask (for HTTP server)
+  * requests (for client)
+Install dependencies:
+<code bash> pip install flask requests </code>
+===== JSON-RPC Server (Python + Flask) =====
+Create a file: //server.py//
+<sxh python>
+from flask import Flask, request, jsonify
+app = Flask(__name__)
+# available RPC methods
+def add(a, b):
+    return a + b
+def subtract(a, b):
+    return a - b
+methods = {
+    "add": add,
+    "subtract": subtract,
+}
+@app.route("/rpc", methods=["POST"])
+def rpc():
+    data = request.get_json()
+    if data.get("jsonrpc") != "2.0":
+        return jsonify(
+            {
+                "jsonrpc": "2.0",
+                "error": {"code": -32600, "message": "Invalid Request"},
+                "id": data.get("id"),
+            }
+        )
+    method_name = data.get("method")
+    params = data.get("params", [])
+    request_id = data.get("id")
+    if method_name not in methods:
+        return jsonify(
+            {
+                "jsonrpc": "2.0",
+                "error": {"code": -32601, "message": "Method not found"},
+                "id": request_id,
+            }
+        )
+    try:
+        result = methods[method_name](*params)
+        return jsonify(
+            {
+                "jsonrpc": "2.0",
+                "result": result,
+                "id": request_id,
+            }
+        )
+    except Exception as e:
+        return jsonify(
+            {
+                "jsonrpc": "2.0",
+                "error": {"code": -32603, "message": str(e)},
+                "id": request_id,
+            }
+        )
+if __name__ == "__main__":
+    app.run(port=5000)
+</sxh>
+Run:
+<code bash> python server.py </code>
+===== JSON-RPC Client (Python) =====
+Create a file: //client.py//
+<sxh python>
+import requests import json
+url = "http://localhost:5000/rpc"
+payload = {
+  "jsonrpc": "2.0",
+  "method": "add",
+  "params": [10, 15],
+  "id": 1
+}
+response = requests.post(url, json=payload)
+print("Status:", response.status_code)
+print("Response:", response.json())
+</sxh>
+Expected output:
+<code> Status: 200 Response: {'jsonrpc': '2.0', 'result': 25, 'id': 1} </code>
+==== Error Codes in JSON-RPC 2.0 ====
+^ Code ^ Meaning ^
+| -32700 | Parse error |
+| -32600 | Invalid Request |
+| -32601 | Method not found |
+| -32602 | Invalid params |
+| -32603 | Internal error |