DECnet Phase IV -to-TCP Industrial Gateway Build

I need a compact, custom gateway that sits between an existing VAX / OpenVMS host (running DECnet Phase IV) and modern Windows-based SCADA software that only understands raw TCP frames. The current middleware is read-only; this replacement must provide full bidirectional READ and WRITE capability so I can both monitor and issue control commands in real time.

Key requirements
• Hardware: x86-class embedded Linux controller (Debian or Yocto are fine as long as the kernel exposes raw sockets).
• Protocol handling: native DECnet Phase IV on one side; raw TCP frames on user-defined port numbers on the other. In addition, it should expose an OPC UA/DA endpoint for external clients that prefer that interface.
• Data scope: “Real Time Data monitoring and control” — essentially numeric process values and discrete control bits that must travel in both directions with minimal latency.
• Functions: Data monitoring and Control operations are mandatory; logging is optional but welcome if it does not add noticeable delay.
• Configuration: node addresses, object numbers, port mappings and tag lists must be editable from a simple text file or web UI.
• Performance: sub-200 ms round-trip for a 256-byte packet under 70 % network load on a 100 Mb link.
• Reliability: watchdog recovery, automatic reconnect on link loss and verbose syslog output for troubleshooting.

Deliverables
1. Compilable C/C++ (or Rust) source code with build script for the target Linux distro.
2. Image or package ready to flash/deploy on the specified controller.
3. User guide covering installation, configuration examples, and a test plan that proves read/write, OPC UA browsing and raw frame forwarding.
4. A small utility or script that stress-tests the gateway against a DECnet simulator so I can validate performance without touching the live plant.

I will provide DECnet object IDs, test VAX login credentials