Unable to get payload response when payload length size is greater than 1000K.(Coap)

Question

I am using Coapthon and Helperclient libraries to get, put, post the data. I am using below mentioned code line to get the payload. it is working fine without any issue if pauload length size is not more than 1000.

response = self.client.get(path_check, timeout=30)

Jun 21, 2020 5:56:11 PM com.coap.dtls.test.ExampleDTLSClient$1 receiveData
INFO: received response, length53, hex payload:

But in some cases payload size is high "length1386", and it failed to get the payload:

Jun 21, 2020 5:56:21 PM com.coap.dtls.test.ExampleDTLSClient$1 receiveData
INFO: received response, length1386, hex payload:

And displays below mentioned error: AttributeError: 'NoneType' object has no attribute 'payload'

Can anyone help he how can I get high length payload? I am using python scripts and copathon libraries to achive it.

response = self.client.get(path_check, timeout=30)

Answer 1

CoAP is limited in its message size to a single UDP packet.

Usually, when the maximum size is exceeded, server and client fall back to what is called block-wise transfer. This allows transferring almost arbitrarily sized payloads.

In this concrete case, it appears on first glance that you are trying to access the response payload as a single response message's .payload , which does not exist because there is no single response message – but the block layer of CoAPython should take care of that. You may have run into a bug in the library implementation, which is easiest discussed at its issue tracker .