臻识车牌识别配制MQTT通讯，解析车号

在物联网项目中，我们的软件与车牌识别通讯，通常使用MQTT通讯更简单。

MQTT配制

测试工具

C# MqttHelper

using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Protocol;
using System;
using System.Collections.Generic;
using YUTU.DAL.Common;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using YUTU.BLL.Global;
using System.Threading;

namespace YUTU.BLL.Common.ClientMidle
{
    public class MqttHelper
    {
        public IMqttClient _mqttClient;
        string serverIP, serverPort, user, pwd;

        public MqttHelper(string ipAddr, string port, string userName, string userPwd)
        {
            serverIP = ipAddr;
            serverPort = port;
            user = userName;
            pwd = userPwd;
        }
        public bool blconntion = false;
        MqttClientOptions options = null;
        public Action GetActionSubscribe;
        public async void ConntionServer() //async
        {
            try
            {
                LogMessage("serverIP[" + serverIP + "]serverPort[" + serverPort + "]user[" + user + "]pwd[" + pwd + "]");
                options = new MqttClientOptions() { ClientId = Guid.NewGuid().ToString("D") };
                options.ChannelOptions = new MqttClientTcpOptions()
                {
                    Server = serverIP,
                    Port = Convert.ToInt32(serverPort)
                };
                options.Credentials = new MqttClientCredentials()
                {
                    Username = user,
                    Password = pwd
                };
                options.CleanSession = true;
                options.KeepAlivePeriod = TimeSpan.FromSeconds(100.5);
                options.KeepAliveSendInterval = TimeSpan.FromSeconds(20000);

                if (null != _mqttClient)
                {
                    await _mqttClient.DisconnectAsync();//await
                    _mqttClient = null;
                }
                _mqttClient = new MqttFactory().CreateMqttClient();

                _mqttClient.ApplicationMessageReceived += (sender, args) =>
                {
                    GetActionSubscribe?.Invoke(Encoding.UTF8.GetString(args.ApplicationMessage.Payload));
                    //ActionSubscribe?.Invoke(Encoding.UTF8.GetString(args.ApplicationMessage.Payload));
                    LogMessage($"ApplicationMessageReceived--ClientID:{args.ClientId} | TOPIC:{args.ApplicationMessage.Topic} | Payload:{Encoding.UTF8.GetString(args.ApplicationMessage.Payload)} | QoS:{args.ApplicationMessage.QualityOfServiceLevel} | Retain:{args.ApplicationMessage.Retain}");

                };

                _mqttClient.Connected += (sender, args) =>
                {
                    LogMessage($"Connected--Client is Connected:  IsSessionPresent:{args.IsSessionPresent}");
                };

                _mqttClient.Disconnected += (sender, args) =>
                {
                    LogMessage($"Client is DisConnected ClientWasConnected:{args.ClientWasConnected}");
                };

                await _mqttClient.ConnectAsync(options);//await
            }
            catch (Exception ex)
            {
                LogMessage("ConntionServer异常:" + ex.Message);
            }
        }

        public async void DisConntionServer()
        {
            try
            {
                LogMessage("开始执行DisConntionServer");
                if (null != _mqttClient && _mqttClient.IsConnected)
                {
                    await _mqttClient.DisconnectAsync();
                    _mqttClient.Dispose();
                    _mqttClient = null;
                }
                LogMessage("执行DisConntionServer成功...");
            }
            catch (Exception ex)
            {
                LogMessage("DisConntionServer异常:" + ex.Message);
            }
        }

        public async void HeartConntionServer()
        {
            try
            {
                LogMessage("开始执行HeartConntionServer");
                if (null != _mqttClient && options != null)
                {
                    await _mqttClient.ConnectAsync(options);
                }
                LogMessage("执行HeartConntionServer成功...");
            }
            catch (Exception ex)
            {
                LogMessage("HeartConntionServer异常:" + ex.Message);
            }
        }

        public void SendMessage(string Topic, string Payload)
        {
            try
            {
                LogMessage("SendMessage---Topic[" + Topic + "]Payload[" + Payload + "]");
                Task.Factory.StartNew(async () =>
                {
                    var msg = new MqttApplicationMessage()
                    {
                        Topic = Topic,
                        Payload = Encoding.UTF8.GetBytes(Payload),

                        QualityOfServiceLevel =
                            (MqttQualityOfServiceLevel)
                                Enum.Parse(typeof(MqttQualityOfServiceLevel), "1"),//Level
                        Retain = false
                    };

                    if (null != _mqttClient)
                    {
                        await _mqttClient.PublishAsync(msg);
                    }
                    else
                    {
                        LogMessage("SendMessage_mqttClient为null");
                    }
                    LogMessage("SendMessage成功:" + Payload);
                });

            }
            catch (Exception ex)
            {
                LogMessage("SendMessage异常:" + ex.Message);
            }
        }

        public async void SubscribeAsync(string Topic)
        {
            try
            {
                LogMessage("SubscribeAsync---Topic[" + Topic + "]");
                if (_mqttClient == null) return;

                Thread.Sleep(1000);
                await _mqttClient.SubscribeAsync(
                 new List
                 {
                    new TopicFilter(
                        Topic,
                        (MqttQualityOfServiceLevel)
                            System.Enum.Parse(typeof (MqttQualityOfServiceLevel), "1"))
                 });
            }
            catch (Exception ex)
            {
                LogMessage("SubscribeAsync异常:" + ex.Message);
            }
        }
    }
}

订阅消息

private MqttHelper _mqttHelper = null;
private static string mqttIP = ConfigurationManager.AppSettings["MqttIP"];
private static string mqttTCPPort = ConfigurationManager.AppSettings["MqttTCPPort"];
private static string mqttUser = ConfigurationManager.AppSettings["MqttUser"];
private static string mqttPwd = ConfigurationManager.AppSettings["MqttPwd"];

public void Init()
{
    try
    {
        //MQTT参数配置
        string ipAddr = mqttIP;
        string port = mqttTCPPort;
        string userName = mqttUser;
        string userPwd = mqttPwd;
        //mqtt消息队列
        _mqttHelper = new MqttHelper(ipAddr, port, userName, userPwd);

    }
    catch (Exception e)
    {
        throw new Exception($"Init异常，{e.Message}");
    }
}

public void TurnOn()
{
    try
    {
        if (_mqttHelper == null)
            throw new Exception("Init异常");
            
        _mqttHelper.ConntionServer();

        //接收订阅消息
        _mqttHelper.GetActionSubscribe = (obj) =>
        {
            var msgObj = JsonConvert.DeserializeObject(obj);
            if (msgObj != null)
            {
                ReceiveMsgCallback?.Invoke(msgObj);
            }
        };

        //订阅消息
        _mqttHelper.SubscribeAsync($"071c55ad-f1a5a757/device/message/up/ivs_result");

        //MQTT心跳
        MessageListenerTimer = new System.Timers.Timer(240000);
        MessageListenerTimer.Elapsed += new ElapsedEventHandler(MessageListenerTimer_Elapsed);
        MessageListenerTimer.Enabled = true;
    }
    catch (Exception e)
    {
        throw new Exception($"TurnOn异常，{e.Message}");
    }
}

public void TurnOff()
{
    try
    {
        MessageListenerTimer.Enabled = false;
        if (_mqttHelper != null)
            _mqttHelper.DisConntionServer();
    }
    catch (Exception e)
    {
        throw new Exception($"TurnOff异常，{e.Message}");
    }
}

解析车号

var license = msgObj.payload.AlarmInfoPlate.result.PlateResult.license;
// 解码车号
string base64License = System.Text.Encoding.UTF8.GetString(Convert.FromBase64String(license));