Extend MQTTnet.Server application.

Source/MQTTnet.Server/Scripts/00_sample.py

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+import json
+
+
+def initialize():
+    """
+    This function is invoked after the script file has been loaded.
+    It will be executed only one time.
+    """
+
+    print("Hello World from Sample script.")
+   
+
+def on_validate_client_connection(context):
+    """
+    This function is invoked whenever a client wants to connect. It can be used to validate the connection.
+    """
+    
+    print(context)
+
+    mqtt_net_server.write_shared_data(context["client_id"], {"custom_value_1": 1, "custom_value_2": True})
+
+    return
+
+    if context["client_id"] != "test_client":
+        context["result"] = "connection_refused_not_authorized"
+        return
+
+    if context["username"] != "bud spencer":
+        context["result"] = "connection_refused_not_authorized"
+        return
+
+    if context["password"] != "secret":
+        context["result"] = "connection_refused_not_authorized"
+
+    print(context)
+
+
+def on_intercept_subscription(context):
+    """
+    This function is invoked whenever a client wants to subscribe to a topic.
+    """
+    
+    print("Client '{client_id}' want's to subscribe to topic '{topic}'.".format(client_id=context["client_id"], topic=context["topic"]))
+
+
+def on_intercept_application_message(context):
+    """
+    This function is invoked for every processed application message. It also allows modifying
+    the message or cancel processing at all.
+    """
+    client_id = context["client_id"]
+
+    if client_id != None:
+        shared_data = mqtt_net_server.read_shared_data(context["client_id"], {})
+        print(shared_data)
+
+    if context["topic"] == "topic_with_response":
+
+        json_payload = {
+            "hello": "world",
+            "x": 1,
+            "y": True,
+            "z": None
+        }
+
+        application_message = {
+            "retain": False,
+            "topic": "reply",
+            "payload": json.dumps(json_payload)
+            }
+
+        mqtt_net_server.publish(application_message)
+
+    print("Client '{client_id}' published topic '{topic}'.".format(client_id=context["client_id"], topic=context["topic"]))

Source/MQTTnet.Server/Scripts/readme.md

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+This directory contains scripts which are loaded by the server and can be used to perform the following tasks.
+
+1. Validation of client connections via credentials, client IDs etc.
+2. Manipulation of every processed message.
+3. Validation of subscription attempts.
+4. Publishing of custom application messages.
+
+All scripts are loaded and _MQTTnet Server_ will invoke functions according to predefined naming conventions.
+If a function is implemented in multiple scripts the context will be moved throug all instances. This allows overriding of results or passing data to other (following) scripts.
+
+The Python starndard library ships with _MQTTnet Server_. But it is possible to add custom paths with Python libraries.
+
+```
+import sys
+sys.path.append(PATH_TO_LIBRARY)
+```
+
+* All scripts must have the file extension _.py_. 
+* All scripts are sorted alphabetically (A to Z) before being loaded and parsed.