Channels and connections

A channel is a message stream on which devices send (publish) and receive (subscribe) data. A channel is part of the MQTT topic: m/<workspace>/c/<channel>.

The channel list

Columns: Name, Route, Tags, Status, and the creation and modification times. A channel without a storage rule is flagged Not stored. Search (name, route, tag, ID), sorting, a status filter, the Display button for choosing columns, pagination (10/20/50/100 rows), Create channel, and Upload CSV are available.

Creating a channel

Field	Description
Name	Required.
Route	Optional. Lowercase letters, digits, and hyphens; unique per workspace; cannot be changed; must not look like a UUID. Used in readable MQTT topics. A channel without a route uses its ID in the topic.
Tags	Press Enter to add. Tags are used for search and for per-tag permissions.
Metadata	A JSON object.

Channel detail

Section	Contents
Settings	Name, tags, status, deletion. The Storage card shows the rules that process this channel. The Metadata tab.
Connections	Connected devices and their type (Publish/Subscribe). The Connect and Disconnect buttons.
Groups	Groups that contain the channel.
Access	Roles and direct policies.
Messages	A shortcut to the Messages page for this channel.
Alarms	Alarms related to this channel.
Journals	Change history.

Channel settings and the Storage card.

A disabled channel does not accept messages. Deleting a channel deletes all its connections.

Device-to-channel connections

A connection is an explicit permission of a device on a channel:

Type	Meaning
Publish	The device may send messages to the channel.
Subscribe	The device may receive messages from the channel (for example commands and configuration).

The Connection section of a channel.

The broker only accepts messages from devices connected with the Publish type, and only forwards messages to devices of the Subscribe type. Connections can be created from the channel detail or the device detail, with multi-select. The rules:

• The connect permission is required on both sides (device and channel).
• Creating an existing connection changes nothing (idempotent).
• At most 100 pairs per request.
• Deleting a device or channel also deletes its connections.
• A sensor behind a gateway does not need its own connection. Only the gateway needs connections (Gateways).
• Connections of a disabled device or channel are kept, but the broker refuses their traffic.

Storing messages

A channel does not store messages by itself

Messages are stored only when an active rule has an Internal DB output. On the Storage card, the Store in Internal DB (SenML) or (JSON) button creates that rule in one click. When a storage rule exists, the card lists the rules that store; when none does, the Not stored flag is shown.

A message without a rule is still received: the device’s Last Seen and latest values keep working, but there is no history.

Retention

Stored messages are kept according to the server policy (365 days by default, compressed after 7 days). The server administrator can change this.