Available Information

The pages of the HiveMQ Control Center have a consistent look and feel. The top of each page provides the title of the page, the user name of the person who is currently logged in, and a Log out option.

The version number of the HiveMQ version that you are currently running appears below the side navigation. Please keep the version information on hand when you contact our support.

To view more information about an item in the control center, click the question mark (?) next to the desired item.

By default, the control center contains the following pages:

Page Description

Dashboard

Shows the current status of HiveMQ and each node in the HiveMQ cluster (including notifications, license information, and key metrics)

License

Provides detailed information on the active and inactive HiveMQ licenses that are associated with the HiveMQ installation

Clients

Overview of all available clients with links to further client details

Retained Messages

Overview of all available retained messages with links to further retained message details

Trace Recordings

Overview of all current trace recordings, with links to create and manage trace recordings

Dropped Messages

Detailed information on dropped messages

Help

Opens the HiveMQ Control Center User Guide (this page)

HiveMQ Enterprise Extensions add additional pages and features to your control center. For more information, see HiveMQ Enterprise Extensions.

Dashboard

The dashboard of the control center provides a clear overview of the current state of HiveMQ and your entire cluster. This information gives you immediate insights on key issues and allows you to quickly check the state of each available cluster node.

Overview of the Dashboard page

At the top of the dashboard, an overview bar shows you key metrics such as the current usage and throughput of the cluster at a glance. For more information on a specific metric, click the metric in the overview bar to open a detail view.


Notifications

The Notifications area of your dashboard displays useful information and alerts. For example, information if a client drops a message. An alert does not necessarily mean that something is wrong. However, an alert can indicate that an unwanted behaviour has occurred.

Notification area with connection-limit alert:

Maximal connections reached

Notification area with connected clients and no alerts:

No important notification

Notification area with no connected clients that displays useful links:

No clientconnected


Active License Information

This area of the control center dashboard shows information about the HiveMQ license that is currenly in use.

License information
Item Description

Connections

The number of connections that are currently in use and the maximum number of connections that the selected license allows

License Type

The validity status and the type of license (for example, valid commercial license)

Maximum Connections

The maximum number of concurrent connections the license that is in use allows

Cluster License

Indicates whether the license enables the use of HiveMQ clusters

Filename

The filename of the license that is currently in use

License Expiration Date

Expiration date of the license that is currently in use

Support Expiration Date

Expiration date of your support subscription

Based on the maximum number of connections the active licence allows, the connections status bar shows the current connection capacity of the selected node:

A green bar indicates that less than 75% of the connections that the active license allows are in use.

Green bar

A yellow bar indicates that more than 75% of the connections that the active license allows are in use.

Yellow bar

A red bar indicates that more than 90% of the connections that the active license allows are in use.

Red bar
If no valid license is availalble in the licence folder of your HiveMQ installation, an evaluation license is used automatically. Evaluation licenses are limited to 25 concurrent connections. For more information, see Evaluation license.
Evaluation license information


Cluster Node Statistics

The statistics area of your control center dashboard shows information for each individual node in your cluster. Nodes are identified with a randomly-generated cluster node ID. An asterik (*) after the cluster node ID indicates the node that is used for the HiveMQ control-center connection.

To view statistics for a node, click the node ID.

Cluster node status of the first node

The following metrics are avaialble for each node in the cluster:

Metric Description

JVM Memory

The amount of the JVM-memory heap space that is in use and the total amount that is avaialable

Disk Space

The amount of disk space where the HiveMQ data folder is located that is in use and the total amount that is available

Running Since

The startup time of the selected node

Total Inbound Publish Messages

The total number of inbound publish messages

Total Outbound Publish Messages

The total number of outbound publish messages

HiveMQ Version

The HiveMQ version the selected node runs

Hostname

The network hostname of the selected node

Total Inbound Volume

The total volume of inbound MQTT messages in bytes

Total Outbound Volume

The total volume of outbound MQTT messages in bytes

Inbound Network Traffic

The amount of inbound MQTT messages per second

Outbound Network Traffic

The amount of outbound MQTT messages per second


Clients

With millions of connected clients, keeping track of specific clients can become a challenge. The HiveMQ Control Center provides tools to list, view, and manage all the MQTT clients known to HiveMQ. Information about subscriptions, connection status, TLS, and more offer detailed insights into every client.


Clients Overview

HiveMQ uses snapshots to display all available MQTT sessions. To view information for the MQTT sessions that are currently available, you must create a fresh snapshot. The HiveMQ snapshot gives you a consolidated view from all of the nodes in your cluster at a particular point in time. This unified snapshot provides an efficient way to sort, filter, and navigate through all of the available MQTT sessions.

To create a snapshot, click Refresh Snapshot. Based on the number of MQTT sessions on your cluster, the refresh process can take a few moments. When the process finishes, an overview table of the current clients displays. To change the order in which the data is sorted on the overview, click the column header. To filter clients by client ID, username, or IP address, select the desired option from the drop-down menus in the Clean Session and Connected columns.

The sorting options and filters that you apply to the Clients overview table are stored until you log out. If you leave the Clients overview and return later, the filters and sorting options that you applied to the overview table remain active.

Snapshots do not update automatically. To manually refresh the data that is shown in the Clients overview table, click Refresh Snapshot.
Clients overview
Column Description

Client ID

The identifier of the client

Clean Session

Indicates whether a client uses a clean session

Connection Status

Indicates whether a client is currently connected

Username

The username of the client. A blank field indicates that no username was set

IP Address

The IP address of the client

The current connection status is illustrated by color. A legend of status states is located at the bottom of the page. To open a client details page for a client and access actions such as disconnecting, subscribing, or un-subscribing, click the identifier of the client in the table.


Client Details

This page displays when you click a client identifier in the Clients overview table.
The client identifier and the connection status of the client for which details are shown appears at the top of the page.

Since HiveMQ 4.3.0, Prev and Next options on your client detail pages allow you to easily navigate through the clients on your Clients overview table. The Prev and Next options on the Client Details page respect the filters and sorting options that you apply to the Clients overview table.

Prev displays information for the client one row before the currently selected entry in the overview table.
Next displays information for the client one row after the currently selected entry in the overview table.

If you change the sorting order or filters of your Clients overview table, the changes that you make are immediately reflected in the Prev and Next information.

Session information

To view more information about each items that is shown on the details page, click the question mark next to the desired column.

For example, more information on Sessions:

Help session


Connection

A central principle of MQTT is the de-coupling of communication partners. De-coupling means that the clients that send and receive the MQTT messages only connect to the MQTT broker. In MQTT, a client never connects directly to another client.
To establish an MQTT connection, the client sends a CONNECT message to the HiveMQ broker and the HiveMQ broker replies to the client with a CONNACK message. The protocol the HiveMQ broker uses used for the connection is TCP.

For more information on MQTT connections, see the Client, Broker, and Connection Establishment post in our MQTT Essentials blog series.
To learn more about the MQTT Keep Alive function, see the Keep Alive and Client Take-Over post.

The Client Detail page provides the following connection information for the client that is currently selected on the overview:

Client connection nformation
Item Description

Client IP

The network IP address of the client. The address can be IPv4 or IPv6

Username

Username of the selected client

Password

Password of the selected client

MQTT Version

The version number of the MQTT protocol that is used for the connection

Keep-Alive

Interval during which the client is required to send control packets. If the client fails to send a packet within the defined interval, the broker disconnects the client.

Listener

The type of listener and the address the client uses to connect to the broker

Connected Node

The unique identifier of the cluster node to which the client is connected

TLS

Transport Layer Security (TLS) is a cryptographic protocol that allows a secure and encrypted communication between a client application and a server at the transport layer. If a TLS listener is enabled in HiveMQ, each client connection for that listener is encrypted and secured by TLS. It is also possible to use an X.509 certificate to authenticate the client. Authentication with an X.509 certificate is an alternative to the username/password authentication.
The TLS column of thew Client Details page shows the most important aspects of the TLS that the selected client uses.

For more information, see Transport Layer Security (TLS).
TLS information
Item Description

TLS Version

The version of the TLS procotol that is used

Cipher Suite

The cipher suite that is used for the encryption of the connection. The cipher suite is a combination of authentication, encryption, message authentication code (MAC), and key exchange algorithms.

X.509 client certificate

The X.509 certificate of the client

To view more information on the cipher suite that the TLS of the selected client uses, click show more:

Cipher suite information

To view more information on the X.509 certificate of the selected client, click show certificate:

Certificate information

Information from the X.509 certificate of the client is divided in two groups, General and Extensions:

Item Description

Common Name

The common name of the owner of the certificate

Organisation

The organisation of the subject

Organisational Unit

The organisational unit of the subject

Serial

The serial number of this certificate

x.509 Version

The version of X.509 certificate

Valid From

The timestamp from which the certificate is valid

Valid Until

The timestamp until which the certificate is valid

Country

The country of the subject

State

The state of the subject

Item Description

Subject Key Identifier

Fingerprint of the key

Last Will

Last will is a feature that is used when a client disconnects ungracefully. The last will of a client publishes a last-will message to a specific topic with a specified Quality of Service upon an ungraceful disconnection.

For more information on the Last Will feature, see Last Will and Testament in our MQTT Essentials series.

When a client connects to the broker, the client can specify a last will message. The will message is a normal MQTT message with a topic, QoS, retained flag, and payload.

LWT section
Item Description

Will Topic

The topic on which the last will payload is published

Will QoS

The Quality of Service level with which the last will message is published

Will Retained

Indicates whether the last will message is a retained message

Will Payload

The payload that is published when the last will is triggered

To view or download the payload of the last-will message, click show payload next to the Will Payload size of the desired payload. This opens a new window:

LWT payload

In the LWT Payload window, you can select how the payload is presented. It is possible to show the payload as a UTF-8 string, hexadecimal value, or binary value. The Content area of the window shows a preview of the payload in the selected format. If desired, you can copy the payload content to your clipboard or download the content as a .dat file.

Restrictions

To ensure a trouble-free communication process, some restrictions have to be observed.

Restrictions
Item Description

Maximum Bytes per Second Inbound

The maximum bytes per second this client can receive from the broker

Maximum Bytes per Second Outbound

The maximum bytes per second this client can send to the broker

Maximum Message Size

The maximum payload size in bytes that MQTT PUBLISH messages sent by this client

Maximum Message Queue Size

The maximum number of messages that the client can store in its message queue on the broker

Drop Strategy for Queued Messages

Defines how the broker manages messages when the message queue limit is reached. Discard: Once the queue size limit is reached, new messages that arrive are dropped. Discard oldest: Once the queue size limit is reached, the oldest message in the queue is dropped when a new message arrives.

Proxy Protocol

HiveMQ supports the PROXY protocol for all listener types. The PROXY protocol is a TCP-based protocol that provides a convenient way to transport client details such as the IP address and port over multiple proxies. If you run your HiveMQ brokers behind a load balancer that proxies the TCP connection, PROXY protocol is helpful. Otherwise, useful client information such as the IP address, port, and SSL information is lost since the broker only recognizes the TCP connection of the load balancer (not of the original client).

Information Proxy Protocol
Item Description

Source IP/Port

The source (origin) IP address and port of the proxy

Destination IP/Port

The destination IP address and port of the proxy

Additional TLVs

The type-length values (TLVs) are key-value pairs that provide optional information such as the SSL X.509 client certificate common names or the TLS version the client used to connect to the proxy.

For more information on the PROXY protocol, see PROXY protocol.

Session

When a client connects to an MQTT broker, the client subscribes to each topic for which it wants to receive messages from the broker. If the client connects to the MQTT broker with a non-persistent session, the broker does not save any subscription information when the client disconnects. In a non-persistent session, each time the client reconnects to the MQTT broker, the client must resubscribe to each topic of interest.

+ In contrast, a persistent session saves all information relevant for the client on the broker. The session is identified by the client ID that the client provides during connection establishment.

For more information, see Persistent Session and Queuing Messages in our MQTT Essentials series.

The following information is stored in the session:

Session information
Item Description

Client ID

Identifies the MQTT client within an MQTT broker or MQTT broker cluster

Clean Session

If set to true, sessions are stateless. Information such as unfinished message flows and subscriptions is lost on disconnect.

Connected/Disconnected Since

Date and time when the client last established or lost connection with the broker

Offline Session TTL

Shows the Time to live (TTL) limit that is set for the client. The TTL timer starts when the client disconnects. If the client does not reconnect within the predefined period, the session is invalidated and the broker deletes all client information (including subscriptions and queued messages). The TTL does not apply while the client is connected

Offline Message Queue Size

When a client with a persistent session is offline (clean-session = false), this entry shows the current number of QoS 1 and 2 messages that are queued for the client

Subscriptions

The Client Detail page provides information on the subscriptions and shared subscriptions of each client. On the detail page, you can add and remove subscription and shared subscription topics for the selected client.

The Subscriptions area shows all topics to which the selected client subscribes. Each subscription consists of a topic and the Quality of Service (QoS) level for the subscription. There are three QoS levels:

  • 0 - At Most Once: Messages are delivered one time only, or not at all.

  • 1 - At Least Once: Messages are delivered at least once, and can be delivered more than once.

  • 2 - Exactly Once: Message delivery is guaranteed, with no duplicates.

Subscription information

Shared Subscriptions

The ability to use shared subscriptions with all versions of MQTT is a unique feature of HiveMQ. Shared subscriptions allow MQTT clients to share the a subscription to the same topic on the broker. In a "standard" MQTT subscription, each client receives a copy of the message. Shared subscriptions distribute the message load of the subscribed topic equally among each client in the shared group. HiveMQ delivers the message to only one subscriber in the group that share the subscription. This mechanism is sometimes called client load balancing.

Shared-subscription information

The shared subscription area shows the topic, shared group name, and QoS level of all shared subscriptions for the selected this client. You can also unsubscribe it by clicking on the x at the right side of each line. Additionally you are able to add new shared subscriptions to this client by inserting the topic, the shared group and the Quality of Service.

For more information, see our MQTT Client Load Balancing with Shared Subscriptions blog post.

Retained Messages

Keeping track of the millions of retained messages that your HiveMQ cluster processes can be a challenge. The HiveMQ Control Center provides the tools you need to manage all the retained messages in your HiveMQ cluster.

Retained Messages Overview

HiveMQ uses snapshots to display all available retained messages. To view information for the retained messages that are currently available, you must create a fresh snapshot. The HiveMQ snapshot gives you a consolidated view from all of the nodes in your cluster at a particular point in time. This unified snapshot provides an efficient way to sort, filter, and navigate through all of the retained messages that are available on your cluster.

To create a snapshot, click Refresh Snapshot. Based on the number of retained messages that are available in your cluster, the refresh process can take a few moments. When the process finishes, an overview table of the retained messages displays. To change the order in which the data is sorted on the overview, click the column header. To filter the messages that are displayed by topic, enter the desired topic in the input field of the Topic column.

The sorting options and filters that you apply to the retained messages overview table are stored until you log out. If you leave the retained messages overview and return later, the filters and sorting options that you applied to the overview table remain active.

Snapshots do not update automatically. To manually refresh the data that is shown in the retained messages overview table, click Refresh Snapshot.
Retained Messages Overview
Column Description

Topic

The topic of the retained message

Payload Size

The size of the payload of the retained message

Creation Date

The date and time when the retained message was created

Retained Message Details

This page displays when you click the topic of a retained message in the Retained Messages overview table. The topic of the retained message for which details are shown appears at the top of the page.

Prev and Next options on each detail page allow you to easily navigate through the retained messages that are listed on your retained messages overview table. The Prev and Next options on the details page respect the filters and sorting options that you apply to the retained messages overview table.

Prev displays detailed information for the message one row before the currently selected entry in the overview table.
Next displays detailed information for the message one row after the currently selected entry in the overview table.

If you change the sorting order or filters on the Retained Messages overview table, the changes are immediately reflected in the Prev and Next information.

Retained Message Detail

The Retained Message Detail page provides message information and user property information for the retained message that is currently selected.

To view more information about each items that is shown on the details page, click the question mark next to the desired column.

Message Information

General

Shows basic information about the retained message that is currently selected.

Item Description

Topic

The topic of the retained message.

QoS

The Quality of Service (QoS) level of the retained message.
There are three QoS levels:
- 0 - At Most Once: Messages are delivered only one time or not at all.
- 1 - At Least Once: Messages are delivered at least one time and can be delivered more than one time.
- 2 - Exactly Once: Message delivery is guaranteed with no duplicates.

Payload Size

The amount of data that the payload of retained message contains in bytes.
NOTE: The payload size does not reflect other data such as user properties or correlation data that the retained message can transmit.

Expiry

Shows when the retained message was created and how long the message is valid.

Item Description

Creation Date

The date and time the retained message was published.

Message Expiry

The message-expiry interval that is set for the retained message. The expiry timer starts at the moment that the retained message is published.

Remaining Time

The time in seconds until the message expires and is deleted from HiveMQ. The time is calculated in seconds at the moment the detail page loads. To recalculate the time until message expiration, click Refresh Page.

Message Metadata

Shows information that is used in a request/response pattern for the retained message. This information is only available for MQTT 5.

Item Description

Response Topic (optional)

The identifier used to implement a request/response pattern between clients.

Correlation Data (optional)

The data used to match response requests to the correct response messages.

Payload Metadata

Shows information about the type and format of the data in the payload of the retained message. This information is only available in MQTT 5.

Item Description

Content Type (optional)

The UTF-8 encoded strings that describe the content of the retained message payload. For example, text/plain.

Payload Format Indicator (optional)

A value that shows whether the message payload contains UTF-8 encoded character data or unspecified bytes.
Only two values are possible:
- 0 - The payload of the retained message is unspecified bytes.
- 1 - The payload of the retained message is well-formed UTF-8 data.

To view more information on the payload of the retained message, click Show Payload.

User Properties

The User Properties area of the details page shows the name and value of all user properties for the retained message. User properties are defined as part of the sender implementation. The meaning of the user properties is not defined by MQTT.
User properties are only available for MQTT 5.

The User Properties area shows a maximum of 500 properties.

Licenses

Your HiveMQ instance can contain more than one license. The license page provides an overview of all HiveMQ license information that is currently avaialble.

Active License

This area shows information about the HiveMQ license that is currenly in use. Only one license can be active at a time. Information for this license is also shown in the Active License Information area of the control center dashboard.

Evaluation license

If no license is is installed in the licence folder of your HiveMQ installation, HiveMQ automatically uses a free evaluation license. Evaluation licenses are limited to 25 concurrent connections:

Evaluation license appearance


Only licenses that are installed on the currently selected node are shown.
Complete view on the license site
Figure 1. License overview

The license table provides the following useful information on the current license:

license_table
Item Description

Maximum Connections

The maximum number of concurrent client connections the license allows

Cluster License

Indicates whether the license enables the use of HiveMQ clusters

Filename

The filename of the current license

Start Date

The date on which the license is activated

License Expiration Date

Expiration date of the license

Support Expiration Date

The expiration date of your support subscription

License Owner

The owner of this license

Contact

Contact information for the owner of the license

Email

Email address of the owner of the license

A warning notification displays at the top of the Active License area when your license is about to expire. The default setting is 30 days before the license expiration date. This time period can be adjusted individually for each license.
expiration warning

If your license expires, an evaluation license is used automatically. Information on the expired license appears in the Inactive licenses area.

License expiration