Adafruit_MQTT_Library/examples/mqtt_arbitrary_data/python_subscriber/subscriber.py
Stuart Feichtinger de426a886f Clean up
2016-02-01 11:08:00 -06:00

115 lines
4.3 KiB
Python

'''MQTT subscriber for Adafruit MQTT library mqtt_arbitrary_buffer example'''
import paho.mqtt.client as mqtt
import argparse
import struct
import array
import sys
return_str =[
"Connection successful",
"incorrect protocol version",
"invalid client identifier",
"server unavailable",
"bad username or password",
"not authorised"
]
args = None
# The callback for when the client receives a CONNACK response from the server.
def on_connect(client, userdata, rc):
"""callback function on connect. Subscribes or exits depending on outcome"""
print("MQTT: "),
print(return_str[rc])
if(rc > 1):
print("Connection refused - " + return_str[rc])
sys.exit(rc)
# Subscribing in on_connect() means that if we lose the connection and
# reconnect then subscriptions will be renewed.
else:
print(return_str[rc])
client.subscribe(args.topic)
print("Subscribed to {}".format(args.topic))
def on_disconnect(client, userdata, rc):
"""Callback for disconnect"""
if rc != 0:
print("Unexpected disconnection.")
client.reconnect()
# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
try:
pMsg = parseMsg(msg.payload)
print("Received char Array: \"{}\", val1: {}, val2: {}, val3: {}...".format(pMsg[0], pMsg[1], pMsg[2], pMsg[3]))
except Exception as err:
print err
def argBegin():
parser = argparse.ArgumentParser(description='MQTT subscriber for Adafruit MQTT library mqtt_arbitrary_buffer example')
parser.add_argument("--host", default="localhost", help='mqtt host to connect to. Defaults to localhost.')
parser.add_argument("-p", "--port", default=1883, help='network port to connect to. Defaults to 1883.')
parser.add_argument("-t", "--topic", nargs='*', default="/feeds/arb_packet", help="mqtt topic to subscribe to. May be repeated multiple times.")
parser.add_argument("-u", "--username", default="testPy", help="provide a username (requires MQTT 3.1 broker)")
parser.add_argument("-P", "--password", default="testPy", help="provide a password (requires MQTT 3.1 broker)")
parser.add_argument("-k", "--keepalive", default=60, help="keep alive in seconds for this client. Defaults to 60.")
return parser.parse_args()
def parseMsg(payload):
"""Parses C struct from MQTT publisher Adafruit MQTT client to Python list"""
arr = array.array('B', payload) #convert python list to C-like array of unsigned char (B)
parsedStruct = struct.Struct('< 10s h L H') #define struct template (see below)
'''
Format of Struct from Adafruit MQTT client, Arduino, etc:
Adafruit MQTT client == Little endian (<)
Var NAME | C TYPE (python symbol) | size of member x bytes
-------------------------------------------------------------------
"charAry" | uchar (s) | 10s x 1 = 10 bytes
"val1" | int16 / short (h) | 1h x 2 = 2 bytes
"val2" | unsigned long (L) | 1L x 4 = 4 bytes
"val3" | uint16/unsigned short(H)| 1H x 2 = 2 bytes
------------------------------------------------------------------
Total packet size = | 18 bytes |
See Section 7.3.2 of Python struct module documentation for complete format list
https://docs.python.org/2/library/struct.html
'''
charAry, val1, val2, val3 = parsedStruct.unpack_from(arr) #convert byte array to formatted struct
charAry = charAry.rstrip(' \t\r\n\0') #remove trailing white space from buffer
return charAry, val1, val2, val3
def main():
"""Wait for incoming message published by Adafruit MQTT client"""
global args
args = argBegin()
client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.username_pw_set(args.username, args.password)
client.connect(args.host, args.port, args.keepalive)
# Blocking call that processes network traffic, dispatches callbacks and
# handles reconnecting.
# Other loop*() functions are available that give a threaded interface and a
# manual interface.
client.loop_forever()
if __name__ == '__main__':
sys.exit(main())