SSE with Leshan LWM2M Demo Server

Question

I am trying to do an http api that interact with a Leshan Demo Server. I was trying to handle the OBSERVE in LWM2M, but I need to handle the notification with http. I discovered that leshan notify using SSE. So I was trying to implement the sse client in python using requests and sseclient.

This is my code:

    response= requests.post(url_request , "format=TLV" , stream= True)    
    client = sseclient.SSEClient(response)
    for event in client.events():
        print(json.loads(event.data))

I tried to run my script but it seems like the stream is not opening and it close immediately without waiting for the answer of the server, even if requests by default implement keep_alive for TCP connection under HTTP and the stream is True.

Does someone know why?

Answer 1

Reading the sseclient documentation, the correct way so use SSEClient seems to be:

from sseclient import SSEClient
messages = SSEClient('http://example.com/sse_stream/')
for msg in messages:
    do_something_useful(msg)

Reading the answer on Leshan Github, the stream URL for Leshan Server Demo seems to be http://your.leshan.server.org/event?ep=your_device_endpoint_name

So I tried that:

from sseclient import SSEClient
messages = SSEClient('http://localhost:8080/event?ep=my_device')
for msg in messages:
    print (msg.event, msg.data)

And it works for me: Getting this kind of results when I observe the temperature instance of Leshan Client Demo :

(u'NOTIFICATION', u'{"ep":"my_device","res":"/3303/0","val":{"id":0,"resources":[{"id":5601,"value":-18.9},{"id":5602,"value":31.2},{"id":5700,"value":-18.4},{"id":5701,"value":"cel"}]}}')
(u'COAPLOG', u'{"timestamp":1592296453808,"incoming":true,"type":"CON","code":"POST","mId":29886,"token":"889372029F81C124","options":"Uri-Path: \\"rd\\", \\"reWfKIgPYD\\"","ep":"my_device"}')
(u'COAPLOG', u'{"timestamp":1592296453809,"incoming":false,"type":"ACK","code":"2.04","mId":29886,"token":"889372029F81C124","ep":"my_device"}')
(u'UPDATED', u'{"registration":{"endpoint":"my_device","registrationId":"reWfKIgPYD","registrationDate":"2020-06-16T10:02:25+02:00","lastUpdate":"2020-06-16T10:34:13+02:00","address":"127.0.0.1:44400","lwM2mVersion":"1.0","lifetime":300,"bindingMode":"U","rootPath":"/","objectLinks":[{"url":"/","attributes":{"rt":"\\"oma.lwm2m\\""}},{"url":"/1/0","attributes":{}},{"url":"/3/0","attributes":{}},{"url":"/6/0","attributes":{}},{"url":"/3303/0","attributes":{}}],"secure":false,"additionalRegistrationAttributes":{}},"update":{"registrationId":"reWfKIgPYD","identity":{"peerAddress":{}},"additionalAttributes":{}}}')
(u'COAPLOG', u'{"timestamp":1592296455150,"incoming":true,"type":"NON","code":"2.05","mId":29887,"token":"3998C5DE2588F835","options":"Content-Format: \\"application/vnd.oma.lwm2m+tlv\\" - Observe: 2979","payload":"Hex:e3164563656ce8164408c03199999999999ae815e108c032e66666666666e815e208403f333333333333","ep":"my_device"}')

If you are interested by notification only, just add a if msg.event == 'NOTIFICATION': block.