Flask return no response

Here's the issue.I was trying to build up a database server using flask deployed on IIS and it is available now.But the issue is after long-time running(maybe 4 or 5 days),the flask server got to return no response without no error!

Is it a bug of Flask or something else? Here's my code. Thank everyone!

from flask import Flask,abort
from flask import jsonify
from flask import request
from flask import make_response
from flask_sqlalchemy import SQLAlchemy
import MySQLdb
import json
from flask_cors import CORS, cross_origin
import time
from datetime import datetime
envdata = []
hard = {
        'ch0':'',
        'ch1':'',
        'ch2':'',
        'ch3':''
        }


app = Flask(__name__, static_url_path='')
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://root:coma@localhost/smart'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)


class enviData(db.Model):

    __tablename__ = 'smartData'
    id = db.Column(db.Integer, primary_key=True, nullable = False, autoincrement = True)
    date = db.Column(db.Integer, nullable = False)
    hour = db.Column(db.Integer, nullable = False)
    minute = db.Column(db.Integer, nullable = False)
    temp = db.Column(db.Integer, nullable = False)
    PM2_5 = db.Column(db.Integer, nullable =False)


    def __init__(self, id, date, hour, minute, temp, PM2_5):
        self.id = id
        self.date = date
        self.hour = hour
        self.minute = minute
        self.temp = temp
        self.PM2_5 = PM2_5

    def __repr__(self):
        return '<ID %r>' % self.id


db.create_all()
@app.route('/')
def welcome():
    return app.send_static_file("index.html")

@app.route('/envidata/', methods = ['POST'])
def add_data():

    if ((not request.json) or (not 'id' in request.json) or (not 'temp' in request.json) or (not 'date' in request.json) or (not 'hour' in request.json) or (not 'minute' in request.json) or (not 'PM2_5' in request.json)):
        abort(400)
    envData = {
        'id': request.json['id'],
        'temp':request.json['temp'],
        'date':request.json['date'],
        'hour':request.json['hour'],
        'minute':request.json['minute'],
        'PM2_5':request.json['PM2_5']
        }
    newestData = {
        'id': request.json['id'],
        'temp':request.json['temp'],
        'date':request.json['date'],
        'hour':request.json['hour'],
        'minute':request.json['minute'],
        'PM2_5':request.json['PM2_5']
        }
    dataE = enviData(int(envData['id']), int(envData['date']), int(envData['hour']), int(envData['minute']), int(envData['temp']), int(envData['PM2_5']))
    db.session.add(dataE)
    db.session.commit()
    return 'Successfully Added!'


@app.route('/hardware/control/', methods = ['POST'])
def hardCtrl():
        if(not request.json):
            abort(400)
        hard.ch0 = request.json['ch0']
        hard.ch1 = request.json['ch1']
        hard.ch2 = request.json['ch2']
        hard.ch3 = request.json['ch3']
        return 'Got your command!'


@app.route('/envidata/date/', methods = ['GET'] )
def get_data_by_date():
    if (not request.args['date']):
        abort(400)
    get_date = request.args['date']
    dates = enviData.query.filter_by(date = get_date)
    i = 0
    buf1 = {}
    data = {}
    for row1 in dates:
        buf1['id'] = row1.id
        buf1['date'] = row1.date
        buf1['hour'] = row1.hour
        buf1['minute'] = row1.minute
        buf1['temp'] = row1.temp
        buf1['PM2_5'] = row1.PM2_5
        data.setdefault(i, buf1)
        i += 1
        buf1 = {}
        row1 = ''
    jsonString = json.dumps(data)
    if len(data) == 0:
        abort(404)
    return jsonString


@app.route('/envidata/hour/', methods = ['GET'])
def get_data_by_hour():
    if (not request.args['hour'] or not request.args['date']):
        abort(400)
    get_hour = request.args['hour']
    get_date = request.args['date']
    hours = enviData.query.filter_by(date = get_date, hour = get_hour).all()
    j = 0
    buf2 = {}
    data = {}
    for row2 in hours:
        buf2['id'] = row2.id
        buf2['date'] = row2.date
        buf2['hour'] = row2.hour
        buf2['minute'] = row2.minute
        buf2['temp'] = row2.temp
        buf2['PM2_5'] = row2.PM2_5
        data.setdefault(j, buf2)
        j += 1
        buf2 = {}
        row2 = ''
    jsonString = json.dumps(data)
    if len(data) == 0:
        abort(404)
    return jsonString


@app.route('/envidata/newest/', methods = ['GET'])
def get_newest_data():
    today = int(time.strftime('%Y%m%d', time.localtime(time.time())))
    get_hour = int(time.strftime('%H', time.localtime(time.time())))
    get_minute = int(time.strftime('%M', time.localtime(time.time())))
    news = enviData.query.filter_by(date = today, hour = get_hour, minute = get_minute).all()
    data = {}
    q = 0
    buf3 = {}
    for row3 in news:
        buf3['id'] = row3.id
        buf3['date'] = row3.date
        buf3['hour'] = row3.hour
        buf3['minute'] = row3.minute
        buf3['temp'] = row3.temp
        buf3['PM2_5'] = row3.PM2_5
        data.setdefault(q, buf3)
        q += 1
        buf3 = {}
        row3 = ''
    jsonString = json.dumps(data)
    if len(data) == 0:
        abort(404)
    return jsonString


@app.route('/hardware/command/', methods = ['GET'])
def get_command():
    command = '00' + str(hard.ch0) + '01' + str(hard.ch1) + '10' + str(hard.ch2) + '11' + str(hard.ch3)
    return command


@app.after_request
def after_request(response):
    response.headers.add('Access-Control-Allow-Origin', '*')
    response.headers.add('Access-Control-Allow-Headers', 'Content-Type,Authorization')
    response.headers.add('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS')
    return response

app.run("120.24.70.93", port=1234)