Python Modbus TCP 读取 input_registers 0x4 获取 MBAP 标头错误

Question

您好，我开发了这段代码，使用 pymodbus 3.4.1 库和 pymodbustcp 0.2.0 库来检查谁工作得更好。

Python 是 Debian 11 的标准，版本为 3.9.2

我激活了两个库的调试：

from pyModbusTCP.client import ModbusClient
c = ModbusClient(host="192.168.1.134", port=1024, unit_id=10, debug=True)

c.open()

if c.is_open == False:
    print('not connected')
else:
    print('connected')

print(c.unit_id)

c.read_input_registers(1,1)

c.close()

from pymodbus.client import ModbusTcpClient
from pymodbus.transaction import ModbusSocketFramer as ModbusFramer


import logging
logging.basicConfig()
log = logging.getLogger()
log.setLevel(logging.DEBUG)

ip = "192.168.1.134"
port_num = 1024
unit_num = 10


client = ModbusTcpClient(ip, port=port_num, framer=ModbusFramer)
client.connect()
rr = client.read_input_registers(1,1, unit=unit_num)
print(rr)

两个库的输出是：

connected
10
Tx
[DD 02 00 00 00 06 0A] 04 00 01 00 01
Rx
[57 65 6C 63 6F 6D 65]
MBAP checking error


DEBUG:pymodbus.logging:Connection to Modbus server established. Socket ('192.168.1.125', 46270)
DEBUG:pymodbus.logging:Current transaction state - IDLE
DEBUG:pymodbus.logging:Running transaction 1
DEBUG:pymodbus.logging:SEND: 0x0 0x1 0x0 0x0 0x0 0x6 0x0 0x4 0x0 0x1 0x0 0x1
DEBUG:pymodbus.logging:New Transaction state "SENDING"
DEBUG:pymodbus.logging:Changing transaction state from "SENDING" to "WAITING FOR REPLY"
DEBUG:pymodbus.logging:Incomplete message received, Expected 28531 bytes Received 19 bytes !!!!
DEBUG:pymodbus.logging:Changing transaction state from "WAITING FOR REPLY" to "PROCESSING REPLY"
DEBUG:pymodbus.logging:RECV: 0x57 0x65 0x6c 0x63 0x6f 0x6d 0x65 0x20 0x74 0x6f 0x20 0x54 0x63 0x70 0x53 0x72 0x76 0xd 0xa
DEBUG:pymodbus.logging:Processing: 0x57 0x65 0x6c 0x63 0x6f 0x6d 0x65 0x20 0x74 0x6f 0x20 0x54 0x63 0x70 0x53 0x72 0x76 0xd 0xa
DEBUG:pymodbus.logging:Frame check failed, ignoring!!
DEBUG:pymodbus.logging:Resetting frame - Current Frame in buffer - 0x57 0x65 0x6c 0x63 0x6f 0x6d 0x65 0x20 0x74 0x6f 0x20 0x54 0x63 0x70 0x53 0x72 0x76 0xd 0xa
DEBUG:pymodbus.logging:Getting transaction 1
DEBUG:pymodbus.logging:Changing transaction state from "PROCESSING REPLY" to "TRANSACTION_COMPLETE"
Modbus Error: [Input/Output] No Response received from the remote slave/Unable to decode response

有人在使用某些机器生产商的某些软件 modbus 服务器时遇到过同样的错误吗？ 欢迎所有建议:)

Answer 1

如果我们接受您收到的回复：

0x57 0x65 0x6c 0x63 0x6f 0x6d 0x65 0x20 0x74 0x6f 0x20 0x54 0x63 0x70 0x53 0x72 0x76 0xd 0xa

并将其渲染为我们得到的 ASCII：

Welcome to TcpSrv

因此，在

1024

处侦听端口

192.168.1.134

的任何设备似乎都不是 Modbus TCP 服务器。由于您没有提供服务器上的任何信息，因此很难说更多（但 Modbus TCP 通常在端口 502 上运行，因此您可能使用了错误的端口）。