def handle_modbus_request(mqtt_client, userdata, message):
"""Process the modbus request"""
logging.debug("In handle_modbus_request")
logging.debug("Payload = %s", message.payload)
#{
# 'ModbusHost': modbus.com:5023
# 'FunctionCode': 5,
# 'UnitID': 2,
# 'StartAddress': 2,
# 'AddressCount': 2,
# 'Data': [2, 3, 4]
# }
logging.debug("message payload = %s", message.payload)
payload = json.loads(message.payload.replace("'", '"'))
if validate_modbus_request(mqtt_client, payload):
modbus_port = payload.get('ModbusPort')
if modbus_port is None or modbus_port == "":
logging.info("Modbus port not specified. Defaulting port to %s",
Defaults.Port)
modbus_port = Defaults.Port
if payload['FunctionCode'] == ModbusFunctionCodes.ReadCoil or \
payload['FunctionCode'] == ModbusFunctionCodes.ReadDiscreteInput or \
payload['FunctionCode'] == ModbusFunctionCodes.ReadHoldingRegisters or \
payload['FunctionCode'] == ModbusFunctionCodes.ReadInputRegisters or \
payload['FunctionCode'] == ModbusFunctionCodes.WriteSingleCoil or \
payload['FunctionCode'] == ModbusFunctionCodes.WriteSingleHoldingRegister or \
payload['FunctionCode'] == ModbusFunctionCodes.WriteMultipleCoils or \
payload['FunctionCode'] == ModbusFunctionCodes.WriteMultipleHoldingRegisters:
#Create a Modbus client and send the modbus request
client = ModbusClient(payload['ModbusHost'], modbus_port)
client.connect()
#Send the modbus request
response = send_modbus_request(client, payload)
logging.debug("response = %s", response)
# close the client
client.close()
if response is not None and response.get('error') is None:
# Publish the modbus response
logging.debug("respData = %s", response)
mqtt.publish_modbus_response(mqtt_client, CB_CONFIG['adapterTopicRoot'], \
create_modbus_response(payload, response))
else:
mqtt.publish_modbus_error(mqtt_client, CB_CONFIG['adapterTopicRoot'], \
create_modbus_error(payload, response.get('error')))
else:
mqtt.publish_modbus_error(mqtt_client, CB_CONFIG['adapterTopicRoot'], \
create_modbus_error(payload, \
"Invalid Modbus function code specified. Unable to process Modbus command."))
logging.debug("Exit handle_modbus_request")
def validate_modbus_request(mqtt_client, payload):
"""Validate the modbus request. Publish any errors if the request is not valid."""
#{
# 'ModbusHost': 'localhost',
# 'ModbusPort': 5023,
# 'FunctionCode': 5,
# 'UnitID': 2,
# 'StartAddress': 2,
# 'AddressCount': 2,
# 'Data': [2, 3, 4]
# }
logging.debug("In validate_modbus_request")
#Validate the ModbusHost value
modbus_host = payload.get('ModbusHost')
if modbus_host is None or modbus_host == "":
logging.debug("Invalid ModbusHost")
mqtt.publish_modbus_error(mqtt_client, CB_CONFIG['adapterTopicRoot'], create_modbus_error(\
payload, "Modbus host not specified. Unable to process Modbus command."))
return False
#Validate the FunctionCode value
func_code = payload.get('FunctionCode')
if func_code is None or func_code == "":
logging.debug("Invalid Modbus FunctionCode")
mqtt.publish_modbus_error(mqtt_client, CB_CONFIG['adapterTopicRoot'], create_modbus_error(\
payload, "Modbus function code not specified. Unable to process Modbus command."))
return False
#Validate the UnitID value
unit_id = payload.get('UnitID')
if unit_id is None or unit_id == "":
logging.debug("Invalid Modbus UnitID")
mqtt.publish_modbus_error(mqtt_client, CB_CONFIG['adapterTopicRoot'], create_modbus_error(\
payload, "Modbus Unit ID not specified. Unable to process Modbus command."))
return False
#Validate the StartAddress value
start_addr = payload.get('StartAddress')
if start_addr is None or start_addr == "":
logging.debug("Invalid Modbus StartAddress")
mqtt.publish_modbus_error(mqtt_client, CB_CONFIG['adapterTopicRoot'], create_modbus_error(\
payload, "Modbus StartAddress not specified. Unable to process Modbus command."))
return False
#Check if a data parameter was specified for write operations
if payload['FunctionCode'] == ModbusFunctionCodes.WriteSingleCoil or \
payload['FunctionCode'] == ModbusFunctionCodes.WriteSingleHoldingRegister or \
payload['FunctionCode'] == ModbusFunctionCodes.WriteMultipleCoils or \
payload['FunctionCode'] == ModbusFunctionCodes.WriteMultipleHoldingRegisters:
data = payload.get('Data')
if data is None or data == "" or len(data) == 0:
logging.debug("Invalid Modbus Data")
mqtt.publish_modbus_error(mqtt_client, CB_CONFIG['adapterTopicRoot'], \
create_modbus_error(\
payload, "Modbus Data not specified. Unable to process Modbus command."))
return False
else:
# Validate the address count length for the write operations
# The count length must be specified if the data array length is greater than 1
addr_count = payload.get('AddressCount')
if (len(data) > 0 and addr_count != len(data)) or addr_count is None or \
addr_count == "":
logging.debug("Invalid Modbus AddressCount")
mqtt.publish_modbus_error(mqtt_client, CB_CONFIG['adapterTopicRoot'], \
create_modbus_error(\
payload, "Modbus address count not specified or invalid. \
Unable to process Modbus command." ))
return False
logging.debug("Exit validate_modbus_request, returning True")
return True