feat: initial release of s4k modbus relay controller v1.0.0-linux

2026-04-21 13:58:54 +02:00 · 2026-04-10 14:00:26 +03:00
commit c3825ff105
5 changed files with 562 additions and 0 deletions
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+MIT License
+
+Copyright (c) 2026 Andrii Syrovatko
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
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+# 🛰 S4K Modbus Relay Control
+
+A lightweight, zero-dependency Python utility for controlling [Ethernet/PoE Modbus Relays](https://www.waveshare.com/wiki/Modbus_POE_ETH_Relay) (specifically tested with Waveshare modules).\
+Designed for stability in production environments where reliability is key.
+
+---
+
+### 📋 Features
+* **Direct Socket Communication:** No heavy libraries like `pymodbus` required.
+* **Instance Protection:** Uses `fcntl` file locking to prevent race conditions during concurrent executions.
+* **Health Checks:** Integrated `ICMP` ping check before command execution.
+* **Configurable:** All parameters (IP, Port, Channels) are stored in an external `.ini` file.
+* **Detailed Logging:** Full audit trail of all `ON/OFF/TOGGLE` actions.
+
+---
+
+### 💻 Requirements
+| Requirement | Value |
+| :--- | :--- |
+| **OS** | Linux (Ubuntu, Debian, LMDE, etc.) |
+| **Python** | 3.6+ |
+| **Permissions** | Write access to log/lock paths |
+
+---
+
+### ⚙️ Configuration (`config.ini`)
+| Section | Parameter | Description | Default |
+| :--- | :--- | :--- | :--- |
+| **`[modbus]`** | `host` | IP address of the relay | `192.168.X.X` |
+| **`[modbus]`** | `port` | TCP port (Waveshare: `4196`) | `4196` |
+| **`[modbus]`** | `unit` | Modbus Unit ID | `1` |
+| **`[modbus]`** | `coil_base` | Channel base num (`0` or `1`) | `1` |
+| **`[modbus]`** | `timeout` | Socket timeout (sec) (only view) | `1` |
+| **`[modbus]`** | `max_channel`| Max channel index (e.g., `7`). `7` for `coil_base=1` too. | `7` |
+| **`[paths]`** | `lock_file` | Path to `.lock` file | `/tmp/modbus.lock` |
+| **`[paths]`** | `log_file`  | Path to `.log` file | `/tmp/modbus.log` |
+
+---
+
+### ⚙️ Installation & Setup
+1. Clone the repository:
+    ```bash
+    git clone https://github.com/andsyrovatko/s4k-modbus-relay-controller.git
+    cd s4k-modbus-relay-controller
+    ```
+2. Configure the tool:
+Copy the example config and edit it with your device details:
+    ```bash
+    cp config.ini.example config.ini
+    nano config.ini
+    ```
+3. Set executable permissions:
+    ```bash
+    chmod +x modbus_controller.py
+    ```
+
+---
+
+### 🚀 Usage
+0. Use via cli or call from another soft:
+
+    ```bash
+    # Get script help/usage info
+    python3 modbus_controller.py
+    # Output: modbus_controller.py <status|on|off|toggle> <channel>
+
+    # Get channel status
+    python3 modbus_controller.py status 8
+    # Output: Channel 8 is OFF
+
+    # Turn a specific channel ON or OFF
+    python3 modbus_controller.py on 8
+    # Output: Channel 8 is turned ON
+
+    # Toggle channel state
+    python3 modbus_controller.py toggle 8
+    # Output: Channel 8 is turned ON
+    ```
+
+---
+
+### ⚠️ Important Note
+[**!IMPORTANT**]\
+This version currently supports Linux only due to the use of fcntl for process locking. Windows support is planned for future releases.
+
+---
+
+### ⚠️ Disclaimer
+> **Use at your own risk!** These scripts are designed for administrative tasks and may perform destructive actions (like killing processes or deleting config files). The author is not responsible for any data loss or system instability. Always test in a sandbox environment first.
+
+---
+
+### ⚖️ License
+This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.
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+[modbus]
+host = 192.168.X.X     # IP address of the Modbus device
+port = 4196            # Port number for the Modbus device
+unit = 1               # Unit ID for the Modbus channel
+coil_base = 1          # Base address for coils (0 for 0-7 channel use, 1 for 1-8 channel use)
+timeout = 1            # Timeout value in seconds
+max_channel = 7        # Maximum number of channels of the Modbus device model (7 - 0-7, as 8 channels summary)
+
+[paths]
+lock_file = /tmp/modbus_controller.lock
+log_file = /tmp/modbus_controller.log
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+#!/usr/bin/env python3
+# =============================================================================
+# Script Name : modbus_controller.py
+# Description : Control Modbus coils via TCP (Modbus RTU over TCP).
+# Usage       : python3 modbus_controller.py <status|on|off|toggle> <channel>
+# Author      : syr4ok (Andrii Syrovatko)
+# Version     : 1.0.0-linux
+# =============================================================================
+import configparser
+import os
+import socket
+import sys
+import time
+import subprocess
+import logging
+import fcntl
+
+# Read configuration (variables will be used later in the code)
+config = configparser.ConfigParser(inline_comment_prefixes=('#', ';'))
+config_path = os.path.join(os.path.dirname(__file__), 'config.ini')
+config.read(config_path)
+
+# Reading variables (with type conversion)
+HOST = config.get('modbus', 'host')
+PORT = config.getint('modbus', 'port')
+UNIT = config.getint('modbus', 'unit')
+COIL_BASE = config.getint('modbus', 'coil_base')
+TIMEOUT = config.getint('modbus', 'timeout')
+MAX_CHANNEL = config.getint('modbus', 'max_channel')
+
+LOCK_FILE = config.get('paths', 'lock_file')
+LOG_FILE = config.get('paths', 'log_file')
+
+log_dir = os.path.dirname(LOG_FILE)
+if not os.path.exists(log_dir):
+    try:
+        os.makedirs(log_dir, exist_ok=True)
+    except OSError as e:
+        print(f"Error: Cannot create log directory {log_dir}: {e}")
+        # Use local log file as instead
+        LOG_FILE = "modbus_controller.log"
+
+logging.basicConfig(
+    filename=LOG_FILE,
+    level=logging.INFO,
+    format="%(asctime)s - %(levelname)s - %(message)s",
+    datefmt="%Y-%m-%d at %H:%M:%S"
+)
+
+lock_fp = open(LOCK_FILE, "w")
+try:
+    fcntl.flock(lock_fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
+except BlockingIOError:
+    print("Another instance is already running.")
+    sys.exit(1)
+
+def is_host_reachable(host):
+    try:
+        result = subprocess.run(
+            ["ping", "-c", "1", "-W", "1", host],
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL
+        )
+        return result.returncode == 0
+    except Exception:
+        return False
+
+def modbus_crc(data):
+    """CALC CRC16 Modbus"""
+    crc = 0xFFFF
+    for a in data:
+        crc ^= a
+        for _ in range(8):
+            if crc & 0x0001:
+                crc = (crc >> 1) ^ 0xA001
+            else:
+                crc >>= 1
+    return crc
+
+def build_write_cmd(channel, state):
+    cmd = [0] * 8
+    cmd[0] = UNIT
+    cmd[1] = 0x05  # Write Single Coil
+    cmd[2] = 0x00
+    cmd[3] = channel
+    cmd[4] = 0xFF if state else 0x00
+    cmd[5] = 0x00
+    crc = modbus_crc(cmd[0:6])
+    cmd[6] = crc & 0xFF
+    cmd[7] = crc >> 8
+    return bytearray(cmd)
+
+def build_read_cmd(channel):
+    cmd = [0] * 8
+    cmd[0] = UNIT
+    cmd[1] = 0x01  # Read Coils
+    cmd[2] = 0x00
+    cmd[3] = channel
+    cmd[4] = 0x00
+    cmd[5] = 0x01
+    crc = modbus_crc(cmd[0:6])
+    cmd[6] = crc & 0xFF
+    cmd[7] = crc >> 8
+    return bytearray(cmd)
+
+def read_status(sock, channel):
+    sock.send(build_read_cmd(channel))
+    try:
+        resp = sock.recv(8)
+        if len(resp) >= 4:
+            return bool(resp[3] & 0x01)
+    except socket.timeout:
+        pass
+    return None
+
+def write_channel(sock, channel, state):
+    sock.send(build_write_cmd(channel, state))
+    time.sleep(0.1)
+
+def toggle_channel(sock, channel):
+    state = read_status(sock, channel)
+    if state is None:
+        print(f"Channel {channel + COIL_BASE} did not respond")
+        return
+    write_channel(sock, channel, not state)
+
+def usage():
+    print(f"Usage: {sys.argv[0]} <status|on|off|toggle> <channel>")
+    sys.exit(1)
+
+if len(sys.argv) != 3:
+    usage()
+
+# Command and channel processing
+command_input = sys.argv[1].lower()
+channel_input = sys.argv[2]
+
+# Converting ON/OFF into a command
+if command_input in ['on', 'off', 'toggle', 'status']:
+    command = command_input
+else:
+    # Attempt to accept "ON"/"OFF" as a command
+    if command_input.upper() == 'ON':
+        command = 'on'
+    elif command_input.upper() == 'OFF':
+        command = 'off'
+    else:
+        usage()
+
+try:
+    channel = int(channel_input) - COIL_BASE
+except ValueError:
+    print("Channel must be an integer")
+    sys.exit(1)
+
+if not (0 <= channel <= MAX_CHANNEL):
+    print(f"Channel must be between {COIL_BASE} and {COIL_BASE + MAX_CHANNEL}")
+    sys.exit(1)
+
+if not is_host_reachable(HOST):
+    error_msg = f"Host Modbus ({HOST}) is not reachable (ping failed)"
+    print(error_msg)
+    logging.error(error_msg)
+    sys.exit(1)
+try:
+    with socket.socket() as s:
+        s.settimeout(TIMEOUT)
+        s.connect((HOST, PORT))
+
+        if command == "status":
+            state = read_status(s, channel)
+            if state is None:
+                print(f"Channel {channel + COIL_BASE} did not respond")
+            else:
+                print(f"Channel {channel + COIL_BASE} is {'ON' if state else 'OFF'}")
+
+        elif command == "on":
+            state_before = read_status(s, channel)
+            if state_before is None:
+                print(f"Channel {channel + COIL_BASE} did not respond")
+            elif state_before:
+                print(f"Channel {channel + COIL_BASE} is already ON, no action taken")
+            else:
+                write_channel(s, channel, True)
+                print(f"Channel {channel + COIL_BASE} is turned ON")
+                logging.info(f"ON command sent to channel {channel + COIL_BASE}")
+        elif command == "off":
+            state_before = read_status(s, channel)
+            if state_before is None:
+                print(f"Channel {channel + COIL_BASE} did not respond")
+            elif not state_before:
+                print(f"Channel {channel + COIL_BASE} is already OFF, no action taken")
+            else:
+                write_channel(s, channel, False)
+                print(f"Channel {channel + COIL_BASE} is turned OFF")
+                logging.info(f"OFF command sent to channel {channel + COIL_BASE}")
+        elif command == "toggle":
+            state_before = read_status(s, channel)
+            toggle_channel(s, channel)
+            if state_before is None:
+                print(f"Channel {channel + COIL_BASE} did not respond")
+            else:
+                print(f"Channel {channel + COIL_BASE} is turned {'OFF' if state_before else 'ON'}")
+                logging.info(f"TOGGLE {'-->OFF' if state_before else '-->ON'} command sent to channel {channel + COIL_BASE}")
+        else:
+            usage()
+except (socket.timeout, ConnectionRefusedError, OSError) as e:
+    error_msg = f"Connection error to host Modbus ({HOST}:{PORT}) - {e}"
+    print(error_msg)
+    logging.error(error_msg)
+    sys.exit(1)
+
+sys.exit(0)