Organizational Automatic vending Machine

#include "mbed.h"
#include "SPI.h"
#include "MQTTEthernet.h"
#include "MQTTClient.h"

#define ECHO_SERVER_PORT   7
 
Serial pc(USBTX, USBRX);   //Enabling the Serial transmission between WIZ750SR and PC.
Serial serial(D1,D0);      // Enabling Serial transmission betwenn Wiz750SR and W7500. 
char c[100]="";

//  for subscribing the data and sending it to the W7500   
//void messageArrived(MQTT::MessageData& md)
//{
//    MQTT::Message &message = md.message;
//    printf("Message arrived: qos %d, retained %d, dup %d, packetid %d\n", message.qos, message.retained, message.dup, message.id);
//    printf("Payload %.*s\n", message.payloadlen, (char*)message.payload);
//    a.printf("%.*s\n", message.payloadlen, (char*)message.payload);
//    pc.printf("%.*s\n", message.payloadlen, (char*)message.payload);
//    //a.printf("%s", (char*)message.payload);
////     pc.printf("%s\n", (char*)message.payload);
//    ++arrivedcount;
//}                                                                  


 
int main(void) {
    printf("Wait a second...\r\n");
    char* topic = "ack";                    //if we are subscribing the acknowledgement.
    MQTTEthernet ipstack = MQTTEthernet();
    
    MQTT::Client<MQTTEthernet, Countdown> client = MQTT::Client<MQTTEthernet, Countdown>(ipstack);
    
    char* hostname = "xxx.xx.xx.x";   //Give the IP Address of the MQTT Broker.
    int port = xxxx;                  // Port number of the MQTT broker.  
    
 
    int rc = ipstack.connect(hostname, port);
    if (rc != 0)
    printf("rc from TCP connect is %d\n", rc);
    printf("Topic: %s\r\n",topic);
    
    MQTTPacket_connectData data = MQTTPacket_connectData_initializer;       
    data.MQTTVersion = 3;
    data.clientID.cstring = "parents";

    if ((rc = client.connect(data)) == 0)
    printf("rc from MQTT connect is %d\n", rc);
   
 //   if ((rc = client.subscribe(topic, MQTT::QOS1, messageArrived)) == 0)
//    printf("rc from MQTT subscribe is %d\n", rc); 
//    client.yield(600000);                                           //  if we need to subscribe acknowledgement
   
   while (true) {
    if (serial.readable()) // if anything available/ readable in Serial port 
    {
        int i;
        c[i]=0;
        for(i=0;i<=10;i++){
        char c1=serial.getc();
        c[i] = c1;
    } 
     pc.printf("The value returned is %s ",c);
     MQTT::Message message;
     char buf[100];
     sprintf(buf, "%s", c);
     message.qos = MQTT::QOS0;
         message.retained = false;
         message.dup = false;

         message.payload = (void*)c;
         message.payloadlen = strlen(c);

         rc = client.publish("balance", message);
         pc.printf("Rc result: %c \n ",rc);
         client.yield(60);
    }
}
}

from flask import Flask, render_template
from flask_socketio import SocketIO
from flask_mqtt import Mqtt
from con_class import PostgresConnection

app = Flask(__name__)
app.config['SECRET'] = 'my secret key'
app.config['TEMPLATES_AUTO_RELOAD'] = True
# app.config['MQTT_BROKER_URL'] = 'broker.hivemq.com'
app.config['MQTT_BROKER_URL'] = '172.16.73.4'
app.config['MQTT_BROKER_PORT'] = 1883
app.config['MQTT_USERNAME'] = ''
app.config['MQTT_PASSWORD'] = ''
app.config['MQTT_KEEPALIVE'] = 5
app.config['MQTT_TLS_ENABLED'] = False


mqtt = Mqtt(app)
socketio = SocketIO(app)

test = 'balance'
mqtt.subscribe(test)

balance = 'balance1'

@mqtt.on_message()
def handle_mqtt_message(client, userdata, message):
    data = dict(
        topic=message.topic,
        payload=message.payload.decode()
    )
    print(data)
    if data['topic'] == test:
        user, cost = data['payload'].split('/')
        obj1 = PostgresConnection()
        cur = obj1.con.cursor()
        cur.execute("SELECT balance FROM public.hello WHERE name=(%s)", (user,))
        res = cur.fetchone()
        print(res[0])
        if cost == 'snack':
            cst = 10
        elif cost == 'drink':
            cst = 15
        else:
            cst = 20
        bal = int(res[0]) - cst
        cur.execute("UPDATE hello SET balance=(%s)  WHERE name=(%s)", (bal, user))
        obj1.con.commit()
        mqtt.publish('ack', 1)
        dat = 'Previous :' + str(res[0]) + '       Cost :' + str(cst) + '            Current :' + str(bal)
        mqtt.publish(balance, dat)


@app.route('/')
def getData():
    obj1 = PostgresConnection()
    cur = obj1.con.cursor()
    cur.execute("SELECT * FROM public.hello")
    res = cur.fetchall()
    return render_template('hello.html', data=res)


if __name__ == '__main__':
    app.run(debug=True, use_reloader=False)

from flask import Flask, render_template, request
import psycopg2
import psycopg2.extras
import pprint

app = Flask(__name__)


class PostgresConnection(object):

    instance = None
    con = None

    def __new__(cls):
        if PostgresConnection.instance is None:
            PostgresConnection.instance = object.__new__(cls)
        return PostgresConnection.instance

    def __init__(self):
        if PostgresConnection.con is None:
            try:
                PostgresConnection.con = psycopg2.connect("dbname=wiznet user=postgres password=postgres")
                print('Database connection opened.')
            except psycopg2.DatabaseError as db_error:
                print("Error :(0)".format(db_error))
        else:
            print(PostgresConnection.con)

    def __del__(self):
        if PostgresConnection.con is not None:
            PostgresConnection.close()
            print('Database connection closed.')


# obj1=PostgresConnection()
# cur=obj1.con.cursor()
# cur.execute("CREATE TABLE student(id serial PRIMARY KEY, name varchar(20), age integer NOT NULL)")
# cur.execute("SELECT * FROM VOTE")
# row= cur.fetchall()
# print(row)

<!DOCTYPE html>
<html lang="en">
<head>
    <!-- meta -->
	<meta http-equiv="content type" content="text/html; charset=utf-8"/>

	<!-- title -->
	<title>Balance</title>

	<!-- css -->
	<!--<link rel="stylesheet" href="main.css" type="text/css" media="screen, projection"/>-->
<!--&lt;!&ndash; Latest compiled and minified CSS &ndash;&gt;-->
    <script>
	document.getElementById("demo").innerHTML = "Update";
</script>
<style>
    ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    background-color: #cfcfcf;
}

li {
    float: left;
}

li a {
    display: block;
    color: white;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
}

li a:hover:not(.active) {
    background-color: #cfcfcf;
}

.active {
    background-color: #4CAF50;
}
</style>
</head>
<ul>
  <li><a class="active" href="#home">HOME</a></li>
  <li><a href="#profile">PROFILE</a></li>
  <li><a href="#add_money">ADD TO BALANCE</a></li>
 </ul>

<h1><center>Organisational Vending machine</center></h1>
<h2><center>Balance Check</center></h2>
<h2><center>Administrator View</center></h2>
<br> </br>
<br> </br>
<table align="center" width="400" cellpadding="20" border="solid black">
    <tr bgcolor=#5a589c>
        <th>User Name</th>
        <th> Current Balance</th>
    </tr>
    {% for item in data %}
    <tr>
        <td align="center">{{item[0]}}</td>
        <td align="center">{{item[1]}}</td>
    </tr>
    {% endfor %}
</table>
</body>
</html>