ModbusTcpClient - Second Request always fails #612
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To add more information for debugging. The issue is not present in 2.4.0 version. Code: try:
client = ModbusClient(self.args['modbus_host'], port=self.args['modbus_port'], timeout= 20)
client.connect()
self.log('connected')
self.log('read input')
input_registers = client.read_input_registers(address=0, count=5)
self.log(input_registers.registers)
# self.log(input_registers.registers)
# client.close()
# self.log('reset')
# rq = ClearCountersRequest()
# rr = client.execute(rq)
# self.log(rr)
self.log('read holding')
# client = ModbusClient(self.args['modbus_host'], port=self.args['modbus_port'])
# client.connect()
holding_registers = client.read_holding_registers(address=0, count=3)
self.log(holding_registers.registers)
client.close()
# self.mqtt_publish("homeassistant/bedroom/light", "ON")
except Exception as inst:
self.error('Modbus error {}'.format(inst))
rq = ReadExceptionStatusRequest(unit=255)
rr = client.execute(rq)
self.log(rr)
self.log(rr.isError())Logs: So this is something within 2.5.0 version. Here's the log for the same code in 2.5.0: |
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@vpetrovych Can you call the requests in a loop and share the logs please? I am not able to reproduce this on my local setup. |
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Just for your reference |
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Same problem here reported on stackoverflow. Code: import pymodbus
from pymodbus.client.sync import ModbusTcpClient
from time import sleep
import logging
FORMAT = ('%(asctime)-15s %(threadName)-15s '
'%(levelname)-8s %(module)-15s:%(lineno)-8s %(message)s')
logging.basicConfig(format=FORMAT)
log = logging.getLogger()
log.setLevel(logging.DEBUG)
connection = False
data = {}
while True:
if not connection:
client = ModbusTcpClient(host="176.219.185.16", port="502")
connection = client.connect()
if connection:
print("connected")
else:
if not client.is_socket_open():
print("connection is broken")
connection = False
data = client.read_holding_registers(address=150,count=10,unit=1).registers
sleep(2)
print(data)pymodbus 2.5.0 LOG pymodbus 2.4.0 LOG |
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@aetasoul and @vpetrovych Refer #614 . This is a basically because |
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Has you can see in the code there is a sleep of two seconds: while True:
if not connection:
client = ModbusTcpClient(host="176.219.185.16", port="502")
connection = client.connect()
if connection:
print("connected")
else:
if not client.is_socket_open():
print("connection is broken")
connection = False
data = client.read_holding_registers(address=150,count=10,unit=1).registers
sleep(2)
print(data)Just to be sure that the problem is not here, I add infinite sleep in the code: import pymodbus
from pymodbus.client.sync import ModbusTcpClient
from time import sleep
import logging
FORMAT = ('%(asctime)-15s %(threadName)-15s '
'%(levelname)-8s %(module)-15s:%(lineno)-8s %(message)s')
logging.basicConfig(format=FORMAT)
log = logging.getLogger()
log.setLevel(logging.DEBUG)
connection = False
data = {}
while True:
sleep(1)
if not connection:
sleep(1)
client = ModbusTcpClient(host="176.219.185.16", port="502")
sleep(1)
connection = client.connect()
sleep(1)
if connection:
sleep(1)
print("connected")
sleep(1)
else:
sleep(1)
if not client.is_socket_open():
sleep(1)
print("connection is broken")
sleep(1)
connection = False
sleep(2)
data = client.read_holding_registers(address=150,count=10,unit=1).registers
sleep(2)
print(data)LOG: |
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@aetasoul can you share the specs for your modbus slave? Also with pymodbus 2.4.0, if you explictly close the connection after each read what is the behaviour ? can you share the logs please ? |
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Specs: let me check if I can find it With pymodbus 2.4.0 if I close the connection after the read the problem is the same as the 2.5.0. But it seems to not be a delay issue, I set the sleep to 10 seconds data = client.read_holding_registers(address=150,count=10,unit=1).registers
client.close()
sleep(10)LOG: |
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@aetasoul Thanks for the experiments, looks like the slave doesn't like the disconnections. Let me make the disconnects optional after a succesfull read. You can expect 2.5.1rc1 in sometime with a patch. |
dhoomakethu
added a commit
that referenced
this issue
Mar 11, 2021
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@aetasoul @vpetrovych |
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Works like a charm 👍 I tried to remove the sleep and works also in this case 👍 Thank you for your help @dhoomakethu !! |
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Pymodbus Specific
Description
What were you trying, what has happened, what went wrong, and what did you expect?
When trying to send 2nd request, an error is returned
[Connection] ModbusTcpClient(192.168.0.15:502): Connection unexpectedly closed 0.000886 seconds into read of 8 bytes without response from unit before it closed connection
It doesn't matter if I read first input and second holding, or vice versa. It always fails the second request.
Removing the ClearCountersRequest also doesn't help
This worked correctly in Node.JS using jsmodbus package, so I have a feeling there could be a bug here.
Code and Logs
logs
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