CoAP server bug

client.py

import asyncio
import aiocoap

@asyncio.coroutine
def observe(protocol, addr):
    host, port = addr
    request = aiocoap.Message(code=aiocoap.GET)
    request.set_request_uri('coap://{}:{}/time'.format(host, port))
    request.opt.observe = 0
    requester = protocol.request(request)
    requester.observation.register_errback(lambda e: print('Error: {!r}'.format(e)))
    requester.observation.register_callback(lambda o: print('Observe: {}'.format(o.payload)))

    try:
        response = yield from requester.response
    except Exception as e:
        print('Failed to fetch resource:\n{!r}'.format(e))
    else:
        print('Result: {}\n{!r}'.format(response.code, response.payload))

@asyncio.coroutine
def create_endpoint(loop, bind_addr):
    factory = lambda: aiocoap.Context(loop=loop)
    _, protocol = yield from loop.create_datagram_endpoint(factory, local_addr=bind_addr)
    yield from protocol.ready
    return protocol

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    protocol = loop.run_until_complete(create_endpoint(loop, ('0.0.0.0', 2000)))
    loop.run_until_complete(observe(protocol, ('127.0.0.1', 5683)))
    loop.run_forever()
    loop.close()

server.py

import asyncio
import aiocoap
import aiocoap.resource as resource
from datetime import datetime

class TimeResource(resource.ObservableResource):
    def __init__(self):
        super(TimeResource, self).__init__()
        self.notify()

    def notify(self):
        self.updated_state()
        asyncio.get_event_loop().call_later(2, self.notify)

    @asyncio.coroutine
    def render_GET(self, request):
        payload = datetime.now().strftime("%Y-%m-%d %H:%M").encode('ascii')
        return aiocoap.Message(code=aiocoap.CONTENT, payload=payload)

def create_site():
    root = resource.Site()
    root.add_resource(('time',), TimeResource())
    return root

@asyncio.coroutine
def create_server(loop, site):
    protofact = lambda: aiocoap.Context(loop, site)
    protocol = yield from aiocoap.Context.create_server_context(site)
    yield from protocol.ready
    return protocol

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    site = create_site()
    protocol = loop.run_until_complete(create_server(loop, site))
    loop.run_forever()
    loop.close()