Modbus Error: [Input/Output] The operation did not complete (read) (_ssl.c:2578)

[alainzhiyanov]

Versions

• Python: 3:10.12
• OS: Ubuntu 22.04
• Pymodbus: 3.7.4

Pymodbus Specific

• Server: async tls
• Client: sync tls

Description

Tried to set up a server and client usint two ec2 instances and have the client write a value to register 0. I get error Modbus Error: [Input/Output] The operation did not complete (read) (_ssl.c:2578). Seems to be a similar issue to this but I am not getting this requested slave does not exist: 0.

Code and Logs

# SERVER
import logging
import asyncio

from pymodbus.server import StartAsyncTlsServer
from pymodbus.device import ModbusDeviceIdentification
from pymodbus.datastore import ModbusSequentialDataBlock, ModbusSlaveContext, ModbusServerContext
import pymodbus

pymodbus.pymodbus_apply_logging_config("DEBUG")


async def run_server():
    store = ModbusSlaveContext(
        di=ModbusSequentialDataBlock(0, [0] * 10),  # Discrete Inputs
        co=ModbusSequentialDataBlock(0, [0] * 10),  # Coils
        ir=ModbusSequentialDataBlock(0, [0] * 10),  # Input Registers
        hr=ModbusSequentialDataBlock(0, [0] * 10),  # Holding Registers
    )
    context = ModbusServerContext(slaves=store, )

    identity = ModbusDeviceIdentification()
    identity.VendorName = "Pymodbus"
    identity.ProductCode = "PM"
    identity.VendorUrl = "http://github.com/bashwork/pymodbus/"
    identity.ProductName = "Pymodbus Server"
    identity.ModelName = "Pymodbus Server"
    identity.MajorMinorRevision = "1.0"


    server = await StartAsyncTlsServer(
        context,
        identity=identity,
        certfile="/certfile.pem",
        keyfile="/key",
        address=("0.0.0.0", 502)
    )


if __name__ == "__main__":
    asyncio.run(run_server(), debug=True)

##client
#!/usr/bin/env python3
import time
import pymodbus
import pymodbus.client as modbusClient
import logging

import ssl


pymodbus.pymodbus_apply_logging_config("DEBUG")
# Hardcoded server IP and port
SERVER_IP = SERVER_IP
SERVER_PORT = 502
sslctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
sslctx.load_cert_chain(certfile="/certfile.pem", keyfile="/key")
sslctx.load_verify_locations(cafile="/certfile.pem")
sslctx.verify_mode = ssl.CERT_OPTIONAL
sslctx.check_hostname = False
# Initialize and connect the client
client = modbusClient.ModbusTlsClient(SERVER_IP, port=SERVER_PORT, timeout=3, sslctx=sslctx, retries = 5)
connection = client.connect()

# Write value 12345 to register 0
register_address = 0
value_to_write = 12345
result = client.write_register(register_address, value_to_write)

time.sleep(1)
read_result = client.read_holding_registers(register_address, count=1)
print(read_result)

# Close the client connection
client.close()

Logs:

[janiversen]

It seems the lower layers closest to the the connection, are you sure your certificates are ok ?

Our test cases includes a case very similar to yours, running a tls server against client_async_calls (all from examples), and that works,

I will try running the 2 examples against each other manually and see if I can reproduce your problem.

[janiversen]

We have made some changes around tls, please try with dev.

[janiversen]

Confirmed this is solved on dev.

[alainzhiyanov]

Thank you for your help. I'm still having an issue. I tried with dev and still getting the same error.

Here's some info about my version (same for both client and server machine):

Here's my log when I run some the example for async tls server and sync tls client:

[janiversen]

I will try to simulate your situation, the sync client have undergone a lot of changes on dev.

[janiversen]

Reproduced.