KivyMD TCP Modbus客户端应用无法从服务器读取数据求助

算力阿峰

2026-8-12

KivyMD TCP Modbus客户端数据读取失败问题排查与解决

我基于教学视频开发了一款KivyMD TCP Modbus客户端应用，服务器连接步骤成功，但进入数据采集页面时出现数据读取失败异常：

Error during data status reading.
Error during data setpoint reading.
Error during data tempOven reading.
Error during data tempOven reading.
Error during data tempOven reading.

手动复刻教学代码，无语法错误但功能异常，以下是完整代码模块，求排查与解决建议：

main.py

from kivymd.app import MDApp
from kivymd.uix.screen import MDScreen
from datacard import CardCoil, CardHoldingRegister, CardInputRegister
from pyModbusTCP.client import ModbusClient
from kivymd.uix.snackbar import Snackbar
from kivy.clock import Clock

class MyWidget(MDScreen):
    """
    Contructor
    """
    def __init__(self,tags,**kwargs):
        self._clientMOD= ModbusClient()
        super().__init__(**kwargs)
        self._tags=tags 
        self._ev=[]   #pt4 min 58
        for tag in self._tags:
            if tag["type"]=="input":
                self.ids.modbus_data.add_widget(CardInputRegister(tag,self._clientMOD))
            elif tag["type"]== "holding":
                self.ids.modbus_data.add_widget(CardHoldingRegister(tag,self._clientMOD))
            elif tag["type"]=="coil":
                self.ids.modbus_data.add_widget(CardCoil(tag,self._clientMOD))
    
    def connect(self):
        if self.ids.bt_con.text== "CONNECT":
            try:
                self.ids.bt_con.text= "DISCONNECT"
                self._clientMOD.host= self.ids.hostname.text
                self._clientMOD.port = int(self.ids.port.text)
                self._clientMOD.open()
                Snackbar(text="Connected succesfully",bg_color=(0,1,0,1)).open()
                self._ev=[]
                for card in self.ids.modbus_data.children:
                    if card.tag['type'] == "holding" or card.tag['type']== "coil":
                        self._ev.append(Clock.schedule_once(card.update_card))
                    else:
                        self._ev.append(Clock.schedule_interval(card.update_card,1))
            except Exception as e:
                print("Erro de conexao com servidor: ", e.args)  
        else:
            self.ids.bt_con.text="CONNECT"
            for event in self._ev:
                event.cancel()
                self._clientMOD.close()
            Snackbar(text="Disconnected",bg_color=(1,0,0,1)).open()


class BasicApp(MDApp):

    __tags=  [{'name':'tempOven','description':'Oven Tempture','unit':'ºC','address':1000,'type':"input"},
              {'name':'setpoint','description':'Desired Tempture','unit':'ºC','address':2000,'type': "holding"},
              {'name':'status','description':'Actuator state','address':1000,'type':"coil"},

    ]
    def build(self):
        self.theme_cls.primary_palette= "Orange"
        self.theme_cls.primary_hue= "700"
        self.theme_cls.accent_palette="Orange"
         
        return MyWidget(self.__tags)

if __name__=='__main__':
    BasicApp().run()

datacard.py

from kivymd.uix.card import MDCard,MDCard
from pyModbusTCP.client import ModbusClient

class DataCard(MDCard):             
    title= "Data Card"
    def __init__(self,tag,mbusClient,**kwargs):
        self.tag= tag                                           
        self.title=self.tag['description']           
        self._mbusclient = mbusClient
        super().__init__(**kwargs)  

    def update_card(self,dt):
        try:
            if self._mbusclient.is_open():
                self.set_data(self._read_data(self.tag['address'],1)[0])
        except Exception as e:
            print("Error during data",self.tag['name'] ,"reading.")

    def write_card(self):
        try:
            if self._mbusclient.is_open():
                self._write_data_fcn(self.tag['address'],self._get_data())
        except Exception as e:
            print("Error during data" ,self.tag['name'] ,"writting.")
    
class CardHoldingRegister(DataCard):
    def __init__(self,tag,mbusClient,**kwargs):
        super().__init__(tag,mbusClient,**kwargs)
        self._read_data=self._mbusclient.read_holding_registers
        self._write_data_fcn= self._mbusclient.write_single_register
    
    def set_data(self, data):
        self.ids.textfield.text= str(data)

    def get_data(self):
        return int(self.ids.textfield.text)
        

class CardInputRegister(DataCard):
    def __init__(self,tag,mbusClient,**kwargs):
        super().__init__(tag,mbusClient,**kwargs)
        self._read_data= self._mbusclient.read_input_registers
    
    def set_data(self, data):
        self.ids.label.text= str(data)
    

class CardCoil(DataCard):
    def __init__(self,tag,mbusClient,**kwargs):
        super().__init__(tag,mbusClient,**kwargs)
        self._read_data= self._mbusclient.read_coils
        self._write_data_fcn= self._mbusclient.write_single_coil

    
    def set_data(self, data):
        self.ids.switch.active= data    #True / False
    
    def get_data(self):
        return self.ids.switch.active                      #RETURN = ajuste

.kv布局文件

#:kivy 1.11.1
<MyWidget>:
    MDBoxLayout:
        orientation:'vertical'
        MDTopAppBar:
            title: "Informatica industrial"
        MDBottomNavigation:
            panel_color: app.theme_cls.accent_color
            text_color_normal:0.4,0.4,0.4,1
            text_color_active:0.8,0.8,0.8,1
            MDBottomNavigationItem:
                name:"config"
                text:"CONFIGURATION"
                icon: "cog"
                MDBoxLayout:
                    orientation: 'vertical'
                    padding: "20p"
                    spacing: "50dp"
                    Image:
                        source:"imgs/modbus.png"
                        pos_hint: {"center_x":0.5,"center_y":0.5}   
                        size_hint: {1,0.2}    
                    MDTextField:
                        id:hostname
                        text:"127.0.0.1"
                        hint_text: "IP Address"
                        size_hint: {0.3, None}
                        height: "60dp"        #tentatativa e erro
                        pos_hint: {"center_x":0.5,"center_y":0.5}
                    MDTextField:
                        id:port
                        text:"502"
                        hint_text: "Port"
                        size_hint: {0.3, None}
                        height: "60dp"       
                        pos_hint: {"center_x":0.5,"center_y":0.4}                        
                    MDRoundFlatIconButton:
                        id: bt_con
                        text:"CONNECT"
                        icon:'connection'
                        pos_hint:{"center_x":0.5,"center_y":0.3} 
                        on_release: root.connect()
                   
            MDBottomNavigationItem:
                name:"data"
                text:"DADOS" 
                icon:"chart-donut"
                ScrollView:
                    size_hint: (1,None)
                    size: 800,600     #define o tamanho como o da janela 800x600
                    bar_pos_y: 'left'
                    bard_width: 20
                    effect_cls: 'ScrollEffect'
                    MDStackLayout:
                        id: modbus_data
                        size_hint: (1, None)
                        padding: 0.05*600,"150dp"
                        spacing: (800/5 - 2*0.05*800)/3
                        adaptive_height: True

<DataCard>:
    orientation: 'vertical'
    padding: '10dp'
    size_hint:None,None
    size: 600/5 , "90dp"
    pos_hint:{"center_x": 0.5, "center_y":0.5}
    MDLabel:
        text: root.title 
        size_hint_y: None
        height:self.texture_size[1]
        pos_hint: {'top':1} 
    MDSeparator:
        height: "1dp"

<CardHoldingRegister>:
    MDTextField:
        id:textfield
        helper_text: "Pressione Enter para enviar os dados"
        helper_text_mode:'persistent'
        multiline: False
        on_text_validate: root.write_card

<CardInputRegister>:
    MDLabel:
        id:label

<CardCoil>:
    MDSwitch:
        id: switch

问题排查与解决建议

Modbus地址偏移修正
pyModbusTCP默认使用0起始地址，但多数Modbus服务器用1起始地址。你的标签地址设置为1000、2000，需要将地址减1后传入读取函数：
修改DataCard的update_card方法：

read_result = self._read_data(self.tag['address'] - 1, 1)

空读取结果处理
当读取失败时，_read_data会返回None，直接取[0]会报错，需先校验结果：

def update_card(self,dt):
    try:
        if self._mbusclient.is_open():
            read_result = self._read_data(self.tag['address'] - 1, 1)
            if read_result and len(read_result) > 0:
                self.set_data(read_result[0])
            else:
                print(f"读取{self.tag['name']}失败：无返回数据")
    except Exception as e:
        print(f"读取{self.tag['name']}出错：{str(e)}")

方法名拼写错误修复
DataCard的write_card方法中调用了不存在的_get_data()，应改为子类定义的get_data()：

def write_card(self):
    try:
        if self._mbusclient.is_open():
            self._write_data_fcn(self.tag['address'] - 1, self.get_data())
    except Exception as e:
        print(f"写入{self.tag['name']}出错：{str(e)}")

调度延迟调整
schedule_once默认立即执行，可能在连接未完全建立时触发读取，添加微小延迟：

self._ev.append(Clock.schedule_once(card.update_card, 0.1))

服务器端验证

确认Modbus服务器运行正常，IP/端口正确，无防火墙拦截
用Modbus Poll等工具验证：1000（或999）地址的输入寄存器、2000（或1999）地址的保持寄存器、1000（或999）地址的线圈寄存器是否可正常访问

内容的提问来源于stack exchange，提问作者caio_alBR

KivyMD TCP Modbus客户端应用无法从服务器读取数据求助

main.py #

datacard.py #

.kv布局文件 #

问题排查与解决建议 #

main.py

datacard.py

.kv布局文件

问题排查与解决建议