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