Python體系結構連接到遠程傳感器

Question

我有一個遠程傳感器，比如測量溫度的Raspberry Pi。 我希望能夠遠程控制此傳感器。

它通過一些未知的手段連接到互聯網，這可以通過Wifi，以太網或GSM/3G。這意味着我無法將靜態IP地址綁定到傳感器，因此無法託管服務器（據我所知）。但它可以很容易地向一個已知的服務器發出請求。我將需要向設備發出請求，獲取數據，告訴它打開/關閉等。但也需要將信息推送到服務器，如日誌等。

我到目前爲止的考慮正在使用Tornado網絡服務器，使用中央服務器來回復HTTP或來自設備的websocket請求，以便爲傳感器訂購和接收數據。這樣做的好處是它很容易設置，但是我覺得我將Tornado扯成了它沒有設計的東西。

另一種可能性是像ZeroMQ或RabbitMQ這樣的消息服務 - 但對我來說，他們看起來更加努力，因爲它們稍微低一點（我需要編寫路由器等），而且感覺過度殺傷。

任何意見或建議，將不勝感激。

Answer 1

這對ZeroMQ應該不會太難。這是我會做的。

在雲中編寫龍捲風HTTP服務器，並結合兩個端口用於zeroMQ PUB和SUB套接字。服務器爲用戶提供REST端點。在樹莓派上，將兩個zeroMQ PUB SUB插座連接到雲服務器。

當您在雲服務器上收到請求時，請在PUB套接字上發送命令。通過zeroMQ SUB套接字在接收到的數據上設置回調。當您收到數據時，在樹莓派上運行您的傳感器代碼。如果有回覆，則通過覆盆子派的PUB頻道發送。在服務器上，回調將回復給用戶。

下面是服務器（雲）和客戶端（樹莓派）的代碼片段來做到這一點。

在雲服務器上運行。

#!/usr/bin/env python 
import json 
import tornado 
import tornado.web 
import zmq 
from tornado import httpserver 
from zmq.eventloop import ioloop 
from zmq.eventloop.zmqstream import ZMQStream 

ioloop.install() 
tornado.ioloop = ioloop 
import sys 


def ping_remote(): 
    """callback to keep the connection with remote server alive while we wait 
    Network routers between raspberry pie and cloud server will close the socket 
    if there is no data exchanged for long time. 
    """ 
    pub_inst.send_json_data(msg="Ping", req_id="##") 
    sys.stdout.write('.') 
    sys.stdout.flush() 


pending_requests = {} 


class ZMQSub(object): 
    def __init__(self, callback): 
     self.callback = callback 
     context = zmq.Context() 
     socket = context.socket(zmq.SUB) 
     # socket.connect('tcp://127.0.0.1:5559') 
     socket.bind('tcp://*:8081') 
     self.stream = ZMQStream(socket) 
     self.stream.on_recv(self.callback) 
     socket.setsockopt(zmq.SUBSCRIBE, "") 

    def shutdown_zmq_sub(self): 
     self.stream.close() 


class ZMQPub(object): 
    def __init__(self): 
     context = zmq.Context() 
     socket = context.socket(zmq.PUB) 
     socket.bind('tcp://*:8082') 
     self.publish_stream = ZMQStream(socket) 

    def send_json_data(self, msg, req_id): 
     topic = str(req_id) 
     self.publish_stream.send_multipart([topic, msg]) 

    def shutdown_zmq_sub(self): 
     self.publish_stream.close() 


def SensorCb(msg): 
    # decode message from raspberry pie and the channel ID. 
    key, msg = (i for i in msg) 
    if not key == "##": 
     msg = json.loads(msg) 

     if key in pending_requests.keys(): 
      req_inst = pending_requests[key] 
      req_inst.write(msg) 
      req_inst.finish() 
      del pending_requests[key] 
     else: 
      print "no such request" 
      print pending_requests 
    else: 
     print "received ping" 


class Handler(tornado.web.RequestHandler): 
    def __init__(self, *args, **kwargs): 
     super(Handler, self).__init__(*args, **kwargs) 

     # get the unique req id 
     self.req_id = str(self.application.req_id) + "#" 
     self.application.req_id += 1 

     # set headers 
     self.set_header("Access-Control-Allow-Origin", "*") 
     self.set_header("Access-Control-Allow-Headers", "x-requested-with") 
     self.set_header('Access-Control-Allow-Methods', 'POST, GET, OPTIONS, PUT') 

    @tornado.web.asynchronous 
    def get(self): 
     print self.request 
     if self.req_id not in pending_requests.keys(): 
      pending_requests[self.req_id] = self 
     else: 
      print "WTF" 
     pub_inst.send_json_data(msg=json.dumps({"op": "ServiceCall"}), req_id=self.req_id) 


if __name__ == "__main__": 
    pub_inst = ZMQPub() 
    sub_inst = ZMQSub(callback=SensorCb) 
    application = tornado.web.Application(
     [(r'/get_sensor_data', Handler), (r'/(.*)')]) 
    application.req_id = 0 
    server = httpserver.HTTPServer(application,) 
    port = 8080 
    server.listen(port) 
    print "Sensor server ready on port: ", port 
    ping = ioloop.PeriodicCallback(ping_remote, 3000) 
    ping.start() 
    tornado.ioloop.IOLoop.instance().start() 

在Raspberry Pie上，運行以下客戶端。

import zmq 
from zmq.eventloop import ioloop 
from zmq.eventloop.zmqstream import ZMQStream 
import sys 

ioloop.install() 


def ping_remote(): 
    """keep pinging the server so that the connection between server and client is not lost""" 
    pub_inst.send_json_data(msg="Ping", req_id="##") 
    sys.stdout.write('.') 
    sys.stdout.flush() 


pending_requests = {} 


class ZMQSub(object): 
    def __init__(self, callback): 
     self.callback = callback 
     context = zmq.Context() 
     socket = context.socket(zmq.SUB) 
     socket.connect('tcp://127.0.0.1:8082') # replace by cloud server's IP address 
     self.stream = ZMQStream(socket) 
     self.stream.on_recv(self.callback) 
     socket.setsockopt(zmq.SUBSCRIBE, "") 

    def shutdown_zmq_sub(self): 
     self.stream.close() 


class ZMQPub(object): 
    def __init__(self): 
     context = zmq.Context() 
     socket = context.socket(zmq.PUB) 
     socket.connect('tcp://127.0.0.1:8081') # replace by cloud server's IP address 
     self.publish_stream = ZMQStream(socket) 

    def send_json_data(self, msg, req_id): 
     topic = str(req_id) 
     self.publish_stream.send_multipart([topic, msg]) 

    def shutdown_zmq_sub(self): 
     self.publish_stream.close() 


def SensorCb(msg): 
    # decode image and the channel ID. 
    key, msg = (i for i in msg) 
    if not key == "##": 
     print key, msg 
     ##### 
     # Do your sensor specific work here. And built a reply for remote server. 
     ##### 
     resp = "response from raspi" 
     pub_inst.send_json_data(msg=resp, req_id=key) 
    else: 
     print "received ping" 


if __name__ == "__main__": 
    pub_inst = ZMQPub() 
    sub_inst = ZMQSub(callback=SensorCb) 
    ioloop.PeriodicCallback(ping_remote, 3000).start() 
    ioloop.IOLoop.instance().start()