02 Connection Setup

Connection Setup

MQTTProbe supports multiple simultaneous MQTT broker connections with persistent configuration.

Creating a Connection

1. Open the Connections panel
2. Click Add Connection to open the connection dialog
3. Configure your connection settings (see below)
4. Click Connect

Connection Settings

Identity

Setting	Description
Name	Friendly name for this connection (must be unique)
Client ID	MQTT client ID (auto-generated if left empty; a session suffix is appended automatically for uniqueness)

Transport

Setting	Description
Protocol	MQTT (TCP) or WebSocket
MQTT Version	3.1.1 (default) or 5.0
Host	Broker hostname or IP address
Port	Broker port (see defaults below)
Username	Authentication username (optional)
Password	Authentication password (optional, stored encrypted)

Port Defaults

Protocol	Plain	TLS
MQTT	1883	8883
WebSocket	8083	8084

TLS

Setting	Description
Use TLS	Enable TLS/SSL encryption
Allow untrusted certificate	Skip certificate validation (not recommended for production)

Warning: "Allow untrusted certificate" disables certificate validation. Only use this for development or testing with self-signed certificates.

WebSocket (additional)

Setting	Description
WebSocket Base Path	Path appended to the WebSocket URL (default: mqtt)

On Connect

Setting	Description
Auto-subscribe topics	Topics to subscribe to immediately after connecting (default: spBv1.0/# for Sparkplug B)

Connection States

State	Description
Disconnected	Not connected
Connecting	Attempting to connect
Connected	Active connection
Failed	Connection attempt failed

Subscriptions

• Maximum 500 subscriptions per connection
• Subscriptions use QoS 1 (At Least Once)
• Topics persist per connection in config/appsettings.json
• Auto-resubscribe reconnects to previously subscribed topics when the connection is restored

Secret Storage

MQTT passwords are never stored in plain text:

• Web host: Encrypted using ASP.NET Data Protection, stored in config/secrets.dat
• MAUI host: Stored in platform-native secure storage (iOS Keychain, Android Keystore, Windows PasswordVault)
• Linux/macOS: Optionally uses the MQTTPROBE_KEK environment variable for AES key encryption

Saving Connections

When you connect, you'll be prompted to save the connection. Saved connections appear in the Connections panel on subsequent launches and can be edited or deleted.

Validation

Connection settings are validated before connecting:

• Name: Cannot be empty
• Host: Must be a valid hostname or IP address
• Port: Must be between 1 and 65535

If validation fails, an error message will appear in the connection dialog.