PAHO-C-1-0-3-RELEASE-NOTES.PDF

This document details the OpenVMS I64 port of the Paho-C MQTT client API, based on the Paho-C 1.0.3 distribution, released in October 2015.

Key Points:

• Purpose: Provides a fully-featured, lightweight MQTT (Message Queuing Telemetry Transport) client for OpenVMS. MQTT is a publish-subscribe protocol over TCP/IP, ideal for remote connections, small code footprints, and low-bandwidth scenarios (e.g., sensors, home automation, mobile apps).
• Features: Supports both synchronous and asynchronous APIs (asynchronous functionality on OpenVMS is achieved using POSIX threads, not ASTs). Includes full SSL/TLS support.
• Requirements: Requires OpenVMS I64 8.4, HP TCP/IP Services V5.7, HP C V7.3-018, and OpenSSL 1.0.1j (statically linked). Developers should have good knowledge of OpenVMS development.
• Installation: The software is distributed as an OpenVMS PCSI kit (VSI-I64VMS-PAHO_C-V0100-3-1.PCSI) and installed using PRODUCT INSTALL PAHO_C. Post-installation, system startup (PAHO$STARTUP.COM) and shutdown (PAHO$SHUTDOWN.COM) scripts need to be integrated into SYS$MANAGER:SYSTARTUP_VMS.COM for system-wide logical name definitions.

• Development & Usage:

  • Logical names are defined for various library variants, such as LIBMQTTV3A$SHR (synchronous, no TLS/SSL) and LIBMQTTV3AS$SHR (asynchronous, with TLS/SSL), to simplify linking.
  • Developers linking application code will need to use the C compiler option /NAMES=(AS_IS,SHORTENED) or appropriate #pragma directives for mixed-case symbols, and include header files from PAHO$ROOT:[INCLUDE].
  • Sample applications are provided in PAHO$ROOT:[EXAMPLES] to demonstrate API usage, requiring access to an MQTT broker.
  • Generally, no special privileges are required, but a high BYTLM quota is recommended, and SYSPRV, BYPASS, or OPER privileges are needed for applications utilizing privileged ports (below 1024).

• Completeness & Future: This OpenVMS port includes all functionality of the Paho-C 1.0.3 API. Future releases may introduce OpenVMS-specific abstraction layers to facilitate usage from other languages like COBOL, FORTRAN, and BASIC.