Erweiterungen

MQTT_README.md

@@ -133,11 +133,34 @@ Payload:
 - User notifications: v1/users/<username>/notifications
 Payload example:
 {
-  "type": "broadcast|notification",
+ "type": "broadcast|notification",
   "message": "...",
   "timestamp": "2025-09-13T22:10:00"
 }
 
+## Chat Messaging (App ↔ Server)
+
+Mobile apps exchange chat messages with the backend through dedicated topics. JSON samples can be
+found under `src/main/resources/mqtt/chat`.
+
+### App → Server
+- **Topic:** `/server/{clientId}/message`
+- **Payload example:** `src/main/resources/mqtt/chat/incoming-chat-message.json`
+- **Required fields:** `sender`, `receiver`, `content`
+- **Optional fields:** `jobId` (Mongo ObjectId), `jobNumber`
+- Payloads missing required fields or containing invalid `jobId` values are rejected with a warning log.
+
+### Server → App
+- **Topic:** `/client/{receiver}/message`
+- **Payload example:** `src/main/resources/mqtt/chat/outgoing-chat-message.json`
+- **Notes:** `direction` (INCOMING/OUTGOING) and `messageType` (GENERAL/JOB_RELATED) mirror the
+  persisted message entity. `read` remains `false` until the receiver acknowledges the message via the
+  REST API.
+
+### Quality of Service
+- Chat topics inherit the global default QoS 2 (`app.mqtt.default-qos`).
+- Messages are not retained; offline clients rely on QoS queueing on the broker.
+
 Quality of Service & Retain
 - QoS 2 (exactly once) is used by default server side for both inbound subscriptions and outbound publications.
 - Retained messages are disabled by default to avoid stale updates.