Consent End User License Agreement (EULA)
Thank you for your interest in our products. We will be happy to provide you with the requested download.
Before downloading the software, please confirm that you have read and accept the End User License Agreement in all points...
Consent End User License Agreement (EULA)
Thank you for your interest in our products. We will be happy to provide you with the requested download.
Before downloading the software, please confirm that you have read and accept the End User License Agreement in all points...
Consent End User License Agreement (EULA)
Thank you for your interest in our products. We will be happy to provide you with the requested download.
Before downloading the software, please confirm that you have read and accept the End User License Agreement in all points...
Before downloading the software, please confirm that you have read and accept the End User License Agreement in all points...
Consent End User License Agreement (EULA)
Thank you for your interest in our products. We will be happy to provide you with the requested download.
Before downloading the software, please confirm that you have read and accept the End User License Agreement in all points...
Before downloading the software, please confirm that you have read and accept the End User License Agreement in all points...
PLCcom for MQTT – Downloads and resources
Here you will find the latest versions of PLCcom for MQTT for .NET and Java, as well as key resources relating to downloads, documentation, the changelog, the data sheet and sample projects.
If you would like to test PLCcom for MQTT, you will need a trial licence. In addition, free trial apps are available for both the MQTT client and the MQTT broker.
.NET Version
PLCcom for MQTT
for integrating MQTT client and broker functions into your own .NET applications
Current version:
2.2.2
Upload date:
03.08.2026
2.2.2
Integrate the required PLCcom MQTT component directly into your .NET project via NuGet.
MQTT Client
MQTT Broker
Examples and getting started:
Open the .NET workshop on GitHub ↗
Java Version
PLCcom for MQTT
for integrating MQTT client and broker functions into your own Java application
Current version:
2.2.2
Upload date:
03.08.2026
2.2.2
Integrate the required PLCcom MQTT components directly into your Java project via Maven. Any client or broker dependencies that are not required can be omitted.
Examples and getting started:
Open the Java workshop on GitHub ↗
PLCcom MQTT Client Tool
Kostenloses Test-Tool
for testing MQTT connections and publish-and-subscribe processes
Current version:
2.2.2
Upload date:
03.08.2026
PLCcom MQTT Broker Tool
Kostenloses Test-Tool
to provide a ready-to-use MQTT broker and for testing with external MQTT clients
Current version:
2.2.2
Upload date:
03.08.2026
SDK – Informations
EU Compliance (CRA)
Cyber Resilience Act (EU 2024/2847)
Changelog PLCcom for MQTT
Version 2.2.2
- Correction to the TLS trust check: Certificates classified as trusted (Trusted Store or known certification authority) are now accepted in accordance with the rules, even for connections via IP addresses.
- Resolution of cyclical connection drops to Java-based MQTT brokers via TLS during keep-alive.
- Standardisation of the PKI certificate store with the PLCcom OPC UA products (folders: own, trusted, issuer, rejected).
Version 2.2.1
- Improvements to stability, error handling and broker compatibility.
- Extension of the MQTT broker’s configuration options to include resource limits and time monitoring for message delivery.
- Extension of the public APIs to include additional convenience features for clients and brokers.
- Further harmonisation of the feature sets of the .NET and Java versions.
- Deployment to the currently supported .NET and Java target platforms.
- Update to the standalone test apps for the MQTT client and broker.
Version 2.1.3 (Java version only)
- Update of the Java components PLCcom MQTT Core, Client and Broker.
- Improvements to stability, error handling and compatibility.
- Revision of the Java workshops and API documentation.
- Update to the standalone test apps for the MQTT client and broker.
- Optimisations to the build, packaging and release processes.
Version 2.1.2
- Updating the packages and artefacts for PLCcom MQTT Core, Client and Broker.
- Extension and standardisation of the MQTT client and broker components for .NET and Java.
- Revision of the public APIs and configuration options.
- Deployment to the currently supported .NET and Java target platforms.
- Updates to the C#, Visual Basic and Java workshops.
- Update to the standalone test apps for the MQTT client and broker.
- Addition of the SBOM and the results of the vulnerability assessment to the release documentation.
- Provision of CRA-relevant product, security and integration documentation for the 2.x product line.
Version 2.1.1
- Standardisation of the joint product range for .NET and Java.
- Consolidation of the client, broker and core components.
- Expanded support for MQTT 3.1.1 and MQTT 5.0.
- Expansion of tests for connection establishment, message processing and faulty MQTT packets.
- Improvements to diagnostics, error handling and configuration.
- Revision of the German and English product documentation.
Version 2.0
- A fundamental overhaul of the MQTT architecture.
- Division into independent Core, Client and Broker components.
- Expansion of the embeddable MQTT broker for direct operation within in-house applications.
- Support for TCP, TLS, WebSocket and Secure WebSocket.
- Expanded support for MQTT 3.1.1 and MQTT 5.0.
- Extended support for QoS levels 0, 1 and 2.
- Enhancement of security features for certificates, authentication and topic-based authorisation.
- Introduction of workshops and standalone test apps for clients and brokers.
Version 1.5.1
- Consolidation of the MQTT components for use in other PLCcom products.
- Standardisation of the project structure for Core, Client and Broker.
- Expansion of automated testing for client, broker and core functions.
- Revision of the joint build and packaging process.
- Improvements to stability, diagnostics and error handling.
Version 1.4.x
- Expansion of broker functions for embedded operation within in-house applications.
- Extension of session and subscription management.
- Improvements to retained messages and message distribution.
- Expansion of support for multiple clients and concurrent connections.
- Expansion of diagnostic and configuration options.
Version 1.3.x
- Expansion of support for MQTT 5.0.
- Extension of the MQTT-5 properties for messages and connections.
- Improvements to QoS processing, Last Will and Retained Messages.
- Extended support for sessions and subscriptions.
- Expansion of internal testing for protocol, connection and error scenarios.
Version 1.2.x
- Extension of the MQTT client functions for publishing and subscribing.
- Expansion of support for QoS 0, 1 and 2.
- Improvements to connection establishment and reconnection.
- Extended support for Last Will and Retained Messages.
- Establishing a common technical foundation for client and broker components.
Version 1.1.2
- Changes to the packaging of the Java artefacts.
- Removing internal build information from the JAR files that are distributed.
- Revision of the signing and release configuration.
- Improvements to the internal publishing process.
- Minor fixes to client, broker and core components.
Version 1.1.1
- Internal package status of the PLCcom MQTT components.
- Provision of basic MQTT client functionality for internal applications.
- Basic support for establishing connections, publishing and subscribing.
- Initial broker functions for internal use.
- Implementation and testing within our own software products.
Version 1.1.0
- Internal development status in preparation for future versions 1.1.x.
- Setting up basic MQTT communication and the initial API structure.
- Initial implementation of connection establishment, publish and subscribe.
- Initial integration and connectivity tests within our own applications.
Documentation PLCcom for MQTT
Latest documentation and examples
Here you will find workshop repositories, API references and PDF documents for PLCcom for MQTT
Workshops on GitHub
API Reference
.NET API Reference: PLCcom for MQTT Java API Reference: MQTT Core (JavaDoc) Java API Reference: MQTT Client (JavaDoc) Java API Reference: MQTT Broker (JavaDoc)
PDF Documents .NET
Getting started with .NET Appendix A – Security Guide .NET Appendix B – MQTT Client Guide .NET Appendix C – MQTT Broker Guide for .NET
PDF Documents Java
You can find the full range of PLCcom for MQTT features here:
Features
PLCcom for MQTT comprises an MQTT client SDK and an embeddable MQTT broker SDK for .NET and Java. The features are categorised by topic below.
SDK and Integration
- MQTT Client SDK for .NET and Java
- Embeddable MQTT broker SDK for .NET and Java
- The client and broker can be used separately or together within the same application
- shared core component for protocol processing, diagnostics, threshold values and certificate management
- Support for MQTT 3.1.1 and MQTT 5.0
- Transport protocols: TCP, TLS, WebSocket and Secure WebSocket
- Fully integrated in-process operation within the application itself
- No separate service, no external broker process and no cloud component required
- No native C or C++ libraries or native protocol wrappers are required
- Multiple MQTT client instances are possible within a single application
- It is possible to run multiple MQTT broker instances within a single process
- blocking and asynchronous client API
- Asynchronous client API using `Task` in .NET and `CompletableFuture` in Java
- High-level builder API, as well as direct publish, subscribe, unsubscribe and receive operations
- configurable connection, operation, read and keep-alive time-outs
- configurable thresholds for packet sizes, queues and other protocol resources
MQTT Client
- Option to select the MQTT protocol version automatically or manually
- Support for MQTT 3.1.1 and MQTT 5.0
- Establishing a connection via mqtt://, mqtts://, ws:// and wss://
- Publish and Subscribe with QoS 0, QoS 1 and QoS 2
- Full QoS processing, including PUBACK, PUBREC, PUBREL and PUBCOMP
- Publishing binary and text-based payloads
- Subscribing to individual topics and topic filters
- Validation of topic names and topic filters
- Support for the topic wildcards + and #
- Unterstützung von Shared Subscriptions über $share//
- Sending, receiving, overwriting and deleting retained messages
- Retain flags on received messages can be analysed
- Last-Will message with Topic, Payload, QoS and Retain
- MQTT-5 properties of the Last-Will message, including Will Delay Interval, Message Expiry Interval, Content Type, Response Topic, Correlation Data, and User Properties
- Clean Start and Session Expiry Interval
- Analysis of the session present information reported by the broker
- MQTT-5-Subscription-Identifier
- MQTT-5-Subscription-Option No Local
- MQTT-5-Subscription-Option Retain As Published
- MQTT-5-Subscription-Option Retain Handling
- MQTT-5 user properties for messages, request/response and last-will messages
- MQTT-5-Payload Format Indicator
- MQTT-5-Content Type
- MQTT-5-Message Expiry Interval
- MQTT-5 response topic and correlation data
- Evaluation of MQTT-5 topic aliases in received messages
- Request/Response as a high-level operation with automatic correlation and timeout
- Receiving messages via a callback handler
- Message reception via blocking receive with a timeout
- optional automatic reconnection
- Exponential backoff during reconnection
- Automatic restoration of registered subscriptions following reconnection
- Username and password authentication
- MQTT-5 Enhanced Authentication during connection establishment
- Authentication using client certificates
- Configurable client ID, keep-alive time and session settings
- JSON convenience functions for publishing and payload evaluation in the .NET version
MQTT Broker
- A fully embeddable MQTT broker for use within a .NET or Java application
- Automatic processing of MQTT 3.1.1 and MQTT 5.0 in accordance with the respective client connection
- Multiple broker listeners running simultaneously within a single broker instance
- Concurrent operation of TCP, TLS, WebSocket and Secure WebSocket listeners
- A dedicated port and a dedicated bind address for each listener
- Custom TLS and client certificate configuration for each listener
- multiple broker instances in the same process
- QoS 0, QoS 1 and QoS 2 for incoming and outgoing messages
- automatic QoS downgrading to the QoS level granted for a subscription
- Saving, overwriting and deleting retained messages
- Automatic delivery of retained messages when a subscription is created
- Last-Will messages, including the Will Delay Interval
- Suppressing the ‘Last Will’ message during a normal DISCONNECT
- Persistent MQTT sessions
- Storing subscriptions within persistent sessions
- Offline queue for clients not connected to the network
- Storing unconfirmed outgoing QoS-1 and QoS-2 messages
- Support and enforcement of the session expiry interval
- Support and enforcement of the Message Expiry Interval
- configurable upper limit for offline queues
- Shared subscriptions with round-robin distribution within a group
- MQTT-5-Subscription-Identifier
- MQTT-5-Subscription-Option No Local
- MQTT-5-Subscription-Option Retain As Published
- MQTT-5-Subscription-Option Retain Handling
- Taking MQTT-5 subscription options into account for retained replay and offline delivery
- MQTT-5 Topic Aliases
- MQTT-5-Receive-Maximum-Flow Control
- configurable maximum packet size
- configurable maximum number of simultaneous connections
- In-process publishing directly from the host application without an additional MQTT client
- In-process listener for receiving messages directly within the host application
- optional delivery of existing retained messages to in-process listeners
- Batch publishing of multiple messages from the host application
- Delivery of in-process messages to local listeners and connected network clients
- Public store interface for custom persistence implementations
- Persistence of retained messages via a custom store implementation
- Persistence of session states via a custom store implementation
- Read-only administration and statistics interface
- Statistics on connections, sessions, subscriptions, queues and retained messages
- resettable broker counters
- JSON convenience functions for publishing and payload evaluation in the .NET version
Custom user, role and permissions systems
- Public Access Validator interface for integrating your own user, role and permissions systems
- Access Validator for .NET via IPlccomMqttBrokerAccessValidator
- Access Validator for Java via PlccomMqttBrokerAccessValidator
- Registering your own validator implementation in the broker options
- Separate access checks for CONNECT, PUBLISH, SUBSCRIBE and UNSUBSCRIBE
- Checking the connection setup against the application’s own rules
- Checking publish permissions based on user, topic and message
- Checking subscribe permissions using user and topic filters
- Checking unsubscribe permissions against the application’s own rules
- Topic-based authorisation for publish and subscribe operations
- It is possible to integrate your own user management systems, databases, role models, claims or directory services
- Integration with customer-specific identity, tenant, or licensing systems is possible.
- Passing the client ID, username, password, protocol version and connection details to your own validation logic
- Assignment of an application-specific Principal object upon successful connection establishment
- Passing the Principal object on to subsequent Publish, Subscribe and Unsubscribe checks
- A user or role can be resolved once during connection setup and reused for subsequent permission checks.
- subsequent reuse of user, role or claim information for topic permissions
- own decision on whether to authorise or reject an MQTT operation
- Returning appropriate MQTT-5 reason codes for rejected operations
- no fixed user or role model
- No dependency on a specific database, user management system or identity solution
Authentication
- Username and password authentication for MQTT clients
- Application-specific validator for username and password
- MQTT-5 Enhanced Authentication for Clients and Brokers
- Public interface for custom MQTT-5 Enhanced Authentication procedures
- Support for application-specific token, challenge or multi-factor authentication methods
- Authentication via client certificates
- Optional or mandatory client certificates per broker listener
- It is possible to combine a TLS client certificate with the application’s own MQTT authentication
TLS and Certificates
- Encrypted MQTT connections via TLS and Secure WebSocket
- Support for server certificates
- Support for client certificates for mutual TLS authentication
- Client certificate modes: None, Optional and Required, per broker listener
- File-based PLCcom PKI store
- separate sections for own, trusted, issued and rejected certificates
- Generating and managing your own certificates
- Importing and using existing certificates
- Importing and using existing private keys
- Validation of the certificate chain
- Checking the hostname and IP address of the remote certificate
- Custom trust anchors and CA certificates can be configured
- Public certificate validator for application-specific certificate verification
- It is possible to make an application-specific decision on whether to accept or reject a certificate
- configurable TLS protocols
- Enforcement of permitted cipher suites on the respective supported target platforms
Custom extensions and persistence
- Public interfaces for extending core broker functions
- own Access Validator implementation
- In-house username and password validation
- own Enhanced Authentication implementation
- in-house certificate validation
- Public Broker Store interface for custom persistence implementations
- In-house storage of retained messages
- In-house storage of persistent sessions
- It is possible to connect to relational or document-based databases via a custom store implementation
- It is possible to integrate the application’s own file, storage or cloud persistence
- public diagnostic listener interface
- Forwarding diagnostic events to a dedicated logging or monitoring system
- no strict dependency on a specific logging framework
Diagnosis and monitoring
- Diagnostic events for client, broker, transport, protocol and security
- Diagnostic events from the broker relating to connection establishment and termination
- Diagnostic events generated by the broker for publish, subscribe and unsubscribe operations
- Diagnostic events relating to TLS connection establishment
- Diagnostic listener with six configurable levels
- Diagnostic level can be switched during operation
- It is possible to integrate diagnostic events into your own logging system
- Read-only access to broker status and statistics
- Analysis of active connections
- Analysis of existing sessions
- Analysis of registered subscriptions
- Analysis of offline queues
- Analysis of existing retained messages
- resettable broker counters
Examples, documentation and test apps
- Comprehensive workshops on MQTT clients and MQTT brokers
- C# examples for .NET
- Visual Basic examples for .NET
- Java examples and workshops
- Free MQTT client tool for testing connections and publish/subscribe processes
- Free MQTT broker tool that can be used directly as a remote server for external MQTT clients
- API Reference for .NET
- separate JavaDoc references for Core, Client and Broker
- Getting Started Guide for .NET and Java
- Security Guides for .NET and Java
- Client Guides for .NET and Java
- Broker Guides for .NET and Java
- GitHub workshop repositories for .NET and Java
Supported .NET target platforms
- .NET Framework 4.7.2
- .NET Framework 4.8
- .NET Standard 2.1
- .NET 8
- .NET 9
- .NET 10
Supported Java target platforms
- Java 11 to Java 26
A wide range of sample programmes and standalone test apps are available to assist you with the development and testing of your software.
Cyber Resilience Act (CRA) – EU compliance documents (EU 2024/2847)
Security contact: [email protected]
PLCcom for MQTT .NET
https://www.indi-an.com/legal/cra/plccom-mqtt-dotnet/2.1.2/eu-declaration-of-conformity.pdf
https://www.indi-an.com/legal/cra/plccom-mqtt-dotnet/2.1.2/security-integration-guide.pdf
https://www.indi-an.com/legal/cra/plccom-mqtt-dotnet/2.1.2/simplified-eu-declaration-of-conformity.pdf
PLCcom for MQTT Java
https://www.indi-an.com/legal/cra/plccom-mqtt-java/2.1.2/eu-declaration-of-conformity.pdf
https://www.indi-an.com/legal/cra/plccom-mqtt-java/2.1.2/security-integration-guide.pdf
https://www.indi-an.com/legal/cra/plccom-mqtt-java/2.1.2/simplified-eu-declaration-of-conformity.pdf
