smartParking/gatewayNode/parking.py

#Authors:   Oulis Evangelos, Oulis Nikolaos, Drosos Katsibras
#===================================================================
#!/usr/bin/env python

import time
import serial
import requests
import json

# Open file to configure communication with server.
with open('/home/pi/project/data.json', 'r') as json_file:
	json_data = json_file.read()

if json_data != "" and json_data != None:
	server_par = json.loads(json_data.replace('\n','').replace(' ',''))
	
	# Initialize server IP and Port to make the connection.
	server_ip = server_par['ip']
	server_port = server_par['port']
	
	if server_ip != None and server_port != None:
		API_ENDPOINT = 'http://' + server_ip + ':' + server_port + '/parkingStatus'
		
		# Initialize Serial Connection with Arduino Uno
		ser = serial.Serial(
			port='/dev/ttyACM0',
			baudrate = 9600,
			parity=serial.PARITY_NONE,
			stopbits=serial.STOPBITS_ONE,
			bytesize=serial.EIGHTBITS,
			timeout=1
		)
		counter=0
		
		ser.readline()
		prev_status = "-1"
		
		# Authentication body content.
		data = """{"username" :""" + server_par['username'] + """, "password":""" + server_par['password'] + """, "device": """ + server_par['device'] + """}"""
		
		# Request to Authenticate Node.
		resp = requests.post(url = API_ENDPOINT, data = data)
		
		# Unpack our data to a JSON object
		data = json.loads(resp.content)
		try:
			# Check if node is Authenticated. "cookie
			if data['cookie'] != None:
				while 1:
					# For a while we request to get Parking Status
					#	witch is a JSON object like [{"no": 1, "status": false}, {"no": 2, "status": true}, ..., {"no": n, "status": true}]
					park_status = ser.readline()
					
					# Substring the input data from arduino.
					#	Data's notation is: <parking_no>#<parking_status>
					park_status_data = str(park_status).split("#")
					
					# Decode and clear serial input data encoding.
					parkingCode = park_status_data[0].replace('b\'','')
					parkingStatus = park_status_data[1].replace('\\r\\n\'', '')
					
					try:
						if parkingStatus != prev_status:
							# If parking status changed from previous status
							#	server would informed about this change.
							data = """{"no":""" + parkingCode + ""","status":""" + parkingStatus + """}"""
							r = s.post(url = API_ENDPOINT, data = data)
							
							# IO : node prints to output the current 
							if parkingStatus == "0":
								print("parking reserved. RESPONSE :", r.status_code, "\n")
							elif parkingStatus == "1":
								print("parking not reserved. RESPONSE : ", r.status_code, "\n")
					except NameError as e:
						print("**Not already prev variable. <Error> : ", str(e), "\n")
					prev_status = parkingStatus
		except TypeError as e:
			print("Node must be authenticate first.")
	else:
		print("Create a *.json configuration like: {'ip' : 'xxx.xxx.xxx.xxx', 'port': 'xxxx'}")