pymodubs TCP 无链接报错: pymodbus.exceptions.ConnectionException: Modbus Error

报错内容

pymodbus.exceptions.ConnectionException: Modbus Error: [Connection] ModbusTcpClient 192.168.2.99:502: Connection unexpectedly closed 0.000 seconds into read of unbounded read bytes without response from slave before it closed connection

背景

• 使用摄像头对下位机持续控制, 第一次发信后成功, 第二次就报错

解决办法

• 每次发信后关闭链接

控制代码

import time
from pymodbus.client import ModbusTcpClient


class WorkstationControl:
    def __init__(self, host, port):
        self.ip_address = host
        self.port = port
        self.client = ModbusTcpClient(host=host, port=port)
        self.delay_time = 2

    def is_connect(self):
        return self.client.connect()

    def start(self):
        self.client.write_register(address=0, value=1)
        # Wait for 2 seconds
        time.sleep(self.delay_time)
        self.client.write_register(address=1, value=0)
        self.client.close()

    def update_speed(self, speed):
        self.client.connect()
        self.client.write_register(address=1, value=speed)
        self.client.close()

    def stop(self):
        self.client.write_register(address=1, value=0)
        # Wait for 2 seconds
        time.sleep(self.delay_time)
        self.client.write_register(address=0, value=2)
        self.client.close()

    def close(self):
        """关闭与 Modbus 服务器的连接"""
        self.client.close()


# 示例用法
if __name__ == '__main__':
    workstation = WorkstationControl(host='192.168.2.99', port=502)
    if workstation.is_connect():
        workstation.start()
        workstation.update_speed(speed=2)
        time.sleep(5)
        workstation.update_speed(speed=3)
        time.sleep(5)
        workstation.stop()
    else:
        print('Failed to connect to the workstation')