VSI-AXPVMS-PAHO C-V0103-0B-1-RNOTES.PDF

This document announces and describes the December 2020 release of the Paho-C MQTT client API for OpenVMS Alpha and Integrity.

The Paho MQTT C API is a fully-featured, lightweight publish-subscribe messaging protocol (based on Paho-C 1.3.0 over TCP/IP) designed for remote, low-bandwidth, and mobile environments. The OpenVMS port includes all functionality of the open-source Paho-C, offering both synchronous and asynchronous APIs (asynchronous via POSIX threads) and full SSL/TLS support.

Key aspects include:

• System Requirements: OpenVMS 8.4-1H1 or later, a TCP/IP stack (VSI, HPE, or MultiNet), VSI C compiler V7.4-001 or comparable, and OpenSSL 1.1.1g (statically linked into the provided shareable images).
• Installation: Provided as an OpenVMS PCSI kit, requiring post-installation steps to configure system-wide logical names that vary based on API type (synchronous/asynchronous) and TLS/SSL support.
• Development: Developers are advised to read Eclipse Paho documentation, use specific C compiler options for mixed-case symbols, and link against appropriate libraries.
• Sample Applications: Example programs are included, but users must explicitly link to the TLS/SSL-enabled shareable images if that functionality is desired.
• New in this Release: Fixes a bug related to network write operations with high maxInflightMessages and an issue with the /DESTINATION qualifier during kit installation.
• Future Plans: While the current release includes all 1.3.0 features, future releases may add OpenVMS-specific abstraction layers for non-C languages like COBOL, FORTRAN, and BASIC.