Host Link Communication Python

A Python client library for KEYENCE KV series PLCs using the Host Link Communication protocol.

This published site intentionally focuses on the recommended high-level helper API:

• HostLinkConnectionOptions
• open_and_connect
• normalize_address
• read_typed
• write_typed
• read_words_single_request
• read_dwords_single_request
• read_words_chunked
• read_dwords_chunked
• write_bit_in_word
• read_named
• poll

Low-level token-oriented client methods are intentionally left out of the published user site and remain repository-maintainer material.

Key Features

• High-level typed reads and writes for U, S, D, L, and F
• Mixed named snapshots with read_named
• Repeated snapshot streaming with poll
• Explicit contiguous helpers for single_request and chunked reads
• Strict lint, type-check, and test coverage in CI

Quick Start

Basic Usage

from hostlink import HostLinkConnectionOptions, open_and_connect, read_named, read_typed, write_typed

async def main() -> None:
    options = HostLinkConnectionOptions(host="192.168.250.100", port=8501)
    async with await open_and_connect(options) as client:
        dm0 = await read_typed(client, "DM0", "U")
        await write_typed(client, "DM10", "U", dm0)

        snapshot = await read_named(client, ["DM0", "DM1:S", "DM2:D", "DM4:F", "DM10.0"])
        print(snapshot)

Documentation

• User Guide
• API Reference
• Performance Guide
• Troubleshooting

Development & CI

This project enforces strict quality standards via run_ci.bat.

Quality Checks

• Linting & Formatting: Ruff
• Type Checking: Mypy
• Unit Testing: Python pytest

Local CI Run

run_ci.bat

Validates the code and builds a standalone CLI tool in the publish/ directory.

License

Distributed under the MIT License.