contrib example: TCP drainage simulator with two devices

examples/contrib/drainage_sim.py

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+#!/usr/bin/env python3
+
+# Simulates two Modbus TCP slave servers:
+#
+# Port 5020: Digital IO (DIO) with 8 discrete inputs and 8 coils. The first two coils each control
+#            a simulated pump. Inputs are not used.
+#
+# Port 5021: Water level meter (WLM) returning the current water level in the input register. It
+#            increases chronologically and decreases rapidly when one or two pumps are active.
+
+import asyncio
+import logging
+from datetime import datetime
+
+from pymodbus.datastore import ModbusSequentialDataBlock, ModbusSlaveContext, ModbusServerContext
+from pymodbus.server import StartAsyncTcpServer
+
+INITIAL_WATER_LEVEL = 300
+WATER_INFLOW = 1
+PUMP_OUTFLOW = 8
+
+logging.basicConfig(level = logging.INFO)
+
+dio_di = ModbusSequentialDataBlock(1, [False] * 8)
+dio_co = ModbusSequentialDataBlock(1, [False] * 8)
+dio_context = ModbusSlaveContext(di = dio_di, co = dio_co)
+wlm_ir = ModbusSequentialDataBlock(1, [INITIAL_WATER_LEVEL])
+wlm_context = ModbusSlaveContext(ir = wlm_ir)
+
+async def update():
+    while True:
+        await asyncio.sleep(1)
+
+        # Update water level based on DIO output values (simulating pumps)
+        water_level = wlm_ir.getValues(1, 1)[0]
+        dio_outputs = dio_co.getValues(1, 2)
+
+        water_level += WATER_INFLOW
+        water_level -= (int(dio_outputs[0]) + int(dio_outputs[1])) * PUMP_OUTFLOW
+        water_level = max(0, min(INITIAL_WATER_LEVEL * 10, water_level))
+        wlm_ir.setValues(1, [water_level])
+
+async def log():
+    while True:
+        await asyncio.sleep(10)
+
+        dio_outputs = dio_co.getValues(1, 8)
+        wlm_level = wlm_ir.getValues(1, 1)[0]
+
+        logging.info(f"{datetime.now()}: WLM water level: {wlm_level}, DIO outputs: {dio_outputs}")
+
+async def run():
+    ctx = ModbusServerContext(slaves = dio_context)
+    dio_server = asyncio.create_task(StartAsyncTcpServer(context = ctx, address = ("0.0.0.0", 5020)))
+    logging.info("Initialising slave server DIO on port 5020")
+
+    ctx = ModbusServerContext(slaves = wlm_context)
+    wlm_server = asyncio.create_task(StartAsyncTcpServer(context = ctx, address = ("0.0.0.0", 5021)))
+    logging.info("Initialising slave server WLM on port 5021")
+
+    update_task = asyncio.create_task(update())
+    logging_task = asyncio.create_task(log())
+
+    logging.info("Init complete")
+    await asyncio.gather(dio_server, wlm_server, update_task, logging_task)
+
+if __name__ == "__main__":
+    asyncio.run(run(), debug=True)