Question

我们希望通过wifi与PLC自动连接。当树莓启动并自动运行他的程序时。它应该是一个独立的覆盆子，所以我们没有键盘或任何东西。我们通过snap7发送数据。这是有效的，但如果wifi断开连接，我会收到此错误：“ISO：在recv TCP期间发生错误：连接超时” 有时在程序开始时我们会收到此错误：“Snap7Exception：TCP：Unreachable peer”

我的程序停止但是我们应该有一些东西，所以我们的wifi再次重新连接而不停止程序。我想我们需要一些东西来捕捉我们的错误并在程序中尝试使用它。

此刻我的节目：

import snap7
import struct
import time
from snap7.snap7exceptions import Snap7Exception
import re
from ctypes import c_int, c_char_p, byref, sizeof, c_uint16, c_int32, c_byte
from ctypes import c_void_p

client = snap7.client.Client()

db_number = 109

print('Press Ctrl-C to quit.')

while True:

    if client.get_connected() == False: 
        client.connect('192.168.5.2', 0, 1) #('IP-address', rack, slot)
        print('not connected')
        time.sleep(0.2)
    else:
        print('connected')

Answer 1

在python中，您可以使用try-except语句捕获错误。

您可以尝试这一行：

while True:

    if client.get_connected() == False:
        try:
            client.connect('192.168.5.2', 0, 1) #('IP-address', rack, slot)
            print('not connected')
            time.sleep(0.2)
        except Snap7Exception as e:
            continue
    else:
        print('connected')

Answer 2

You could use try-exception for connecting and reading the PLC, such as below code:

from time import sleep
from snap7 import client as s7


def plc_connect(ip, rack, slot, stop_tries, freq):
    plc = s7.Client()
    tries = 1
    while tries < stop_tries and not plc.get_connected():
        try:
            print('trying for connecting to PLC ...')
            sleep(freq)
            plc.connect(ip, rack, slot)
            return True

        except Exception as e:
            logger.error("warning in PLC connection >>{}".format(e))
            sleep(freq)

            if tries == (stop_tries - 1):
                print('error in plc connection')
                return False

        tries += 1
    return False


def data_reader():
    plc = s7.Client()
    try:
        result, data_items = plc.read_multi_vars(data_items)
        return result, data_items
    except Exception as e:
        print('warning:>>{}'.format(e))

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2 个答案: