Sending a json payload from a CoAP server as return value to GET method using CoAPthon library

Question

I am using CoAPthon to create a server, it should return a json payload whenever the get method is invoked, below is my code snippet:

from coapthon.resources.resource import Resource
from coapthon.server.coap import CoAP 
import json

class res(Resource):
   def __init__(self,name="Res",coap_server=None):
      super(res,self).__init__(name,coap_server,visible=True,observable=True,allow_children=True)
      with open("/home/pratik/Iot_datamodels/IoT-openiot-DataModels/oic.r.temperature.json","r") as f:
        value = json.load(f)
      self.payload=value['definitions']
      self.resource_type = "oic.r.temperature"
      self.content_type = "application/json"
      self.interface_type = "oic.if.a"

   def render_GET(self,request):
    print json.dumps({"e":[{ "n": "temperature", "v":23.5,"u":"degC" }]})
    return json.dumps({"e":[{ "n": "temperature", "v":23.5,"u":"degC" }]}))

class CoAPServer(CoAP):
  def __init__(self, host, port, multicast=False):
    CoAP.__init__(self,(host,port),multicast)
    self.add_resource('sens-Me/',res())
    print "CoAP server started on {}:{}".format(str(host),str(port))
    print self.root.dump()

def main():
    ip = "0.0.0.0"
    port = 5683
    multicast=False
    server = CoAPServer(ip,port,multicast)
    try:
        server.listen(10)
    except KeyboardInterrupt:
        server.close()

if __name__=="__main__":
  main()

The server runs, and I can see it by visiting the IP address from copper. But when I press get, I get 5.00 Internal Server Error(Blockwise) on my browser. Could someone suggest me how to do it?

Answer 1

first import the following

from coapthon import defines

then redefine get function inside class res as follows :-

def render_GET(self,request):
   self.payload = (defines.Content_types["application/json"],json.dumps({"e":[{ "n": "temperature", "v":23.5,"u":"degC" }]}))
   return self