继续自动搜索连接snap7

Question

我们想通过无线网络与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。这是可行的，但是如果wifi正在断开连接，我会得到以下错误："ISO:在recv :连接超时期间发生的错误“--有时在程序开始时我们会得到这个错误："Snap7Exception: TCP: Unreachable”

我的程序停止了，但是我们应该有一些东西，这样我们的wifi就可以在不停止程序的情况下重新连接。我想我们需要一些东西来捕捉我们的错误，并在一个尝试或什么程序中使用这个。

我现在的节目：

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，可以使用try-except语句捕获错误。

您可以沿着这条线尝试一些东西：

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

您可以使用try-exception连接和读取PLC，如下面的代码：

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))

Answer 3

import time

import snap7
from snap7.exceptions import Snap7Exception

# client = snap7.client.Client()
connect = False


def dataPLC(client_):
    print(client_.db_read(100, 10, 4))
    time.sleep(2)


while True:

    if not connect:
        try:
            client = snap7.client.Client()
            client.connect('172.20.255.200', 0, 2)
            time.sleep(1)
            connect = client.get_connected()
            print('plc connect ', connect)
        except Snap7Exception as e:
            connect = False
            continue
    else:
        try:
            if connect:
                print('connection')
                dataPLC(client)

        except Snap7Exception as e:
            client.destroy()
            print('error ', e)
            connect = False
            continue