Mosquitto V2.0-22 for OpenVMS

Thank your for your interest in this port of the Mosquitto MQTT broker to OpenVMS. The current release of Mosquitto for OpenVMS is based on the Mosquitto V2.0-22 distribution.

Mosquitto is an open source (EPL/EDL licensed) message broker that implements the MQTT protocol versions 5.0, 3.1.1, and 3.1. MQTT is a lightweight messaging protocol based on the publish–subscribe model that operates over TCP/IP. It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium. For example, it has been used in sensors communicating to a broker via satellite link, over occasional dial-up connections with healthcare providers, and in a range of home automation and small device scenarios. It is also ideal for mobile applications because of its small size, low power usage, minimized data packets, and efficient distribution of information to one or many receivers. The MQTT publish-subscribe messaging pattern requires a message broker, which is responsible for distributing messages to interested clients based on the topic of a message.

This OpenVMS port of the Mosquitto broker includes all functionality provided by the Open-Source release, including SSL/TLS support, bridging, client authentication, and access controls. Additional information about the Mosquitto broker and MQTT in general can be found at http://mosquitto.org and http://mqtt.org respectively.

VMS Software Inc. acknowledges the Mosquitto development team for their ongoing efforts in developing and supporting this software, which demands considerable time and dedication.

For a detailed description of the features and bug fixes included in this release, please read https://mosquitto.org/blog/2025/07/version-2-0-22-released/.

This release also includes a simple OpenVMS-specific plugin that provides the ability for the Mosquitto broker to authenticate users via standard OpenVMS means (namely checking the supplied credentials against those in SYSUAF).

SSL/TLS support is statically linked into the broker and uses OpenSSL V3.0.

The kit you are receiving has been compiled and built using the operating system and compiler versions listed below. Although the kit is expected to perform correctly on systems with newer versions of the operating system or products listed, VSI cannot guarantee successful installation or operation on older versions.

In addition to the above requirements, it is assumed that the reader has a solid understanding of OpenVMS and its software development environment.

Before using the Mosquitto broker, it is recommended that users read the documentation available at http://mosquitto.org/documentation/ in order to better understand how to configure and manage the broker.

The kit is provided as an OpenVMS PCSI kit that can be installed by a suitably privileged user with the following command:

$ PRODUCT INSTALL MOSQUITTO

The installation will then proceed as follows (output may differ slightly from that shown, depending on platform and other factors):

Performing product kit validation of signed kits ...

The following product has been selected:
    VSI I64VMS MOSQUITTO V2.0-22           Layered Product

Do you want to continue? [YES]

Configuration phase starting ...

You will be asked to choose options, if any, for each selected product and
for any products that may be installed to satisfy software dependency requirements.

Configuring VSI I64VMS MOSQUITTO V2.0-22: Mosquitto for OpenVMS is based on Mosquitto Version 2.0-22

    © Copyright 2025 VMS Software Inc.

    VSI Software Inc.

* This product does not have any configuration options.

Execution phase starting ...

The following product will be installed to destination:
    VSI I64VMS MOSQUITTO V2.0-22           DISK$I64SYS:[VMS$COMMON.]

Portion done: 0%...10%...20%...30%...50%...70%...80%...90%...100%

The following product has been installed:
    VSI I64VMS MOSQUITTO V2.0-22           Layered Product

VSI I64VMS MOSQUITTO V2.0-22: Mosquitto for OpenVMS is based on Mosquitto Version 2.0-22

    Post-installation tasks are required.

    To start Mosquitto at system boot time, add the following lines to
    SYS$MANAGER:SYSTARTUP_VMS.COM:

        $ file := SYS$STARTUP:MOSQUITTO$STARTUP.COM
        $ if f$search("''file'") .nes. "" then @'file'

    To shutdown Mosquitto at system shutdown, add the following lines
    to SYS$MANAGER:SYSHUTDWN.COM:

        $ file := SYS$STARTUP:MOSQUITTO$SHUTDOWN.COM
        $ if f$search("''file'") .nes. "" then @'file'

$ @SYS$STARTUP:MOSQUITO$STARTUP CLIENT

Maxjobs:         0  Fillm:       256  Bytlm:       128000
Maxacctjobs:     0  Shrfillm:      0  Pbytlm:           0
Maxdetach:       0  BIOlm:       150  JTquota:       4096
Prclm:          50  DIOlm:       150  WSdef:         4096
Prio:            4  ASTlm:       300  WSquo:         8192
Queprio:         4  TQElm:       100  WSextent:     16384
CPU:        (none)  Enqlm:      4000  Pgflquo:     256000

The shareable image MOSQUITTO$ROOT:[LIB]MOSQUITTO$AUTH_PLUGIN_VMS.EXE is a simple plugin for the Mosquitto MQTT broker that provides the ability for the broker to authenticate users via standard OpenVMS means (namely checking the supplied credentials against those in SYSUAF). Note that the plugin presently verifies only credential validation, ensuring that a valid username and password are supplied. It does not provide authorization or access control for authenticated users once connected to the broker; such functionality will be introduced in a future release.

# Authentication plugin (specify path to OpenVMS shareable image)
auth_plugin mosquitto$auth_plugin_vms

The example program code is clearly organized and well-commented, allowing you to adapt it to your needs with minimal reference to the API documentation.

Depending on your TCP/IP configuration it may be necessary to explicitly specify a value in MOSQUITTO$ROOT:[CONF]MOSQUITTO.CONF for the listener parameter.