diff --git a/assethandler.py b/assethandler.py
index a96017a..9fbe2ac 100755
--- a/assethandler.py
+++ b/assethandler.py
@@ -4,6 +4,12 @@ import uuid
 import aioserial
 import aiomqtt
 import pyubx2
+import json
+from paho.mqtt.properties import Properties
+from paho.mqtt.packettypes import PacketTypes
+import paho.mqtt.client as mqtt
+
+from command import Command
 
 BAUD = 115200
 
@@ -31,11 +37,20 @@ class SerialMQTTHandler:
         # MQTT client
         self.client_id = f"{handler_id}-{uuid.uuid4()}"
         self.mqtt_client = aiomqtt.Client(
-            mqtt_host, port=mqtt_port, identifier=self.client_id
+            mqtt_host, port=mqtt_port, identifier=self.client_id, protocol=mqtt.MQTTv5
         )
 
         # Topic base
         self.topic_base = f"asset/{handler_id}"
+        self.command_topic = f"{self.topic_base}/command"
+
+        # Add an arbitrary command
+        self.commands = {}
+
+        example_command = Command(
+            "example-cmd", {"type": "number"}, description="An example command"
+        )
+        self.commands[example_command.name] = example_command
 
     async def parse_serial(self):
         buffer = bytearray()
@@ -74,27 +89,40 @@ class SerialMQTTHandler:
                         continue
                     topic = f"{self.topic_base}/{parsed.identity}/{name}"
                     await self.mqtt_client.publish(topic, value, qos=1, retain=True)
-            else:
-                print(parsed)
-
-            await self.mqtt_client.publish(f"{self.topic_base}/raw", raw)
-            await self.mqtt_client.publish(f"{self.topic_base}/parsed", str(parsed))
 
     async def mqtt_command_writer_task(self):
-        command_topic = f"{self.topic_base}/command"
         async for message in self.mqtt_client.messages:
             topic = str(message.topic)
-            if topic == command_topic:
-                await self.ser.write_async(message.payload)
+            payload = message.payload.decode("utf-8")
+            payload = json.loads(payload)
+            if topic.startswith(self.command_topic):
+                #await self.ser.write_async(message.payload)
+                command_name = topic.removeprefix(f"{self.command_topic}/")
+                command = self.commands.get(command_name)
+                if command is not None:
+                    print(topic, payload, "valid:", command.validate(payload), message.properties)
+
+                    if message.properties is not None and message.properties.ResponseTopic is not None:
+                        await self.mqtt_client.publish(message.properties.ResponseTopic, message.payload, qos=1)
+                else:
+                    print("Unknown command:", topic, message.payload)
 
     async def run(self):
-        command_topic = f"{self.topic_base}/command"
         interval = 5
 
         while True:
             try:
                 async with self.mqtt_client as client:
-                    await client.subscribe(command_topic)
+                    await client.subscribe(f"{self.command_topic}/+")
+
+                    for command in self.commands.values():
+                        props = Properties(PacketTypes.PUBLISH)
+                        props.ResponseTopic = "asset/client/response"
+                        props.CorrelationData = b"req-42"
+
+                        await self.mqtt_client.publish(f"{self.command_topic}/{command.name}/schema", str(command.schema), qos=1, retain=True, properties=props)
+                        for k,v in command.additional_properties.items():
+                            await self.mqtt_client.publish(f"{self.command_topic}/{command.name}/{k}", str(v), qos=1, retain=True)
 
                     await asyncio.gather(
                         self.serial_reader_task(),
diff --git a/command.py b/command.py
new file mode 100644
index 0000000..e93827f
--- /dev/null
+++ b/command.py
@@ -0,0 +1,15 @@
+import jsonschema
+
+
+class Command:
+    def __init__(self, name: str, schema, **kwargs):
+        self.name = name
+        self.schema = schema
+        self.additional_properties = kwargs
+
+        self._validator = jsonschema.validators.validator_for(
+            schema, default=jsonschema.validators.Draft7Validator
+        )(schema=schema)
+
+    def validate(self, o) -> bool:
+        return self._validator.is_valid(o)
diff --git a/requirements.txt b/requirements.txt
index f9f43a4..38b568f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,3 +3,4 @@ aioserial
 black
 pyubx2
 pyubxutils
+jsonschema