This module implements a CoAp Server and Client, operating as both at the same time.
from network import WLAN
from network import Coap
import uselect
import _thread
# The callback that handles the responses generated from the requests sent to a CoAp Server
def response_callback(code, id_param, type_param, token, payload):
print("Code: {}".format(code))
# The ID can be used to pair the requests with the responses
print("ID: {}".format(id_param))
print("Type: {}".format(type_param))
print("Token: {}".format(token))
print("Payload: {}".format(payload))
# Thread handling the sockets
def socket_thread(p, coap_socket):
while True:
# Wait for any socket to become available
sockets = p.poll()
for s in sockets:
sock = s[0]
event = s[1]
if(event & uselect.POLLIN):
# Check if the socket belongs to the CoAp module
if(sock == coap_socket):
# Call Coap.read() which parses the incoming CoAp message
Coap.read()
# Connect to the network
wlan = WLAN(mode=WLAN.STA)
wlan.connect('your-ssid', auth=(WLAN.WPA2, 'your-key'))
# Initialise the CoAp module
Coap.init(str(wlan.ifconfig()[0]), service_discovery=True)
# Add a resource with a default value and a plain text content format
r = Coap.add_resource("resource1", media_type=Coap.MEDIATYPE_TEXT_PLAIN, value="default_value")
# Add an attribute to the resource
r.add_attribute("title", "resource1")
# Add an attribute to the resource
r.add_attribute("ct", str(Coap.MEDIATYPE_TEXT_PLAIN))
# Configure the possible operations on the resource
r.callback(Coap.REQUEST_GET | Coap.REQUEST_POST | Coap.REQUEST_PUT, True)
# Add a resource without default value, XML content format and E-Tag enabled
r = Coap.add_resource("resource2", media_type=Coap.MEDIATYPE_APP_XML, etag=True)
# Configure the possible operations on the resource
r.callback(Coap.REQUEST_GET | Coap.REQUEST_POST | Coap.REQUEST_PUT | Coap.REQUEST_DELETE, True)
# Register the response handler for the requests that the module initiates as a CoAp Client
Coap.register_response_handler(response_callback)
# Get the UDP socket created for the CoAp module
coap_server_socket = Coap.socket()
# Create a new poll object
p = uselect.poll()
# Register the CoAp module's socket to the poll
p.register(coap_server_socket, uselect.POLLIN | uselect.POLLHUP | uselect.POLLERR)
# Start a new thread which will handle the sockets of "p" poll
_thread.start_new_thread(socket_thread, (p, coap_server_socket))
# Send a request to a CoAp server
id = Coap.send_request("192.168.0.234", Coap.REQUEST_GET, uri_port=5683, uri_path=".well-known/core", payload="payload", token="token1", include_options=True)
print(id)
Initialize the CoAp module.
The arguments are:
address
is the address where the CoAp module handles communication.port
is the port where the CoAp module listens. If not set, the default CoAp UDP port is 5683.service_discovery
is a Boolean argument that enables/disables service discovery. If enabled, the CoAp module will listen on the CoAp multicast address: 224.0.1.187. This is disabled by default.Returns with the socket assigned to the given address and port during Coap.init() (= assigned to the CoAp module).
Creates a resource object and adds it to the CoAp module to operate as a server.
uri
is the full path of the resource.media_type
is the media type (CoAp option: Content-Format) of the resource. If not given, no defined media type is associated with the resource.max_age
is the maximum time in seconds that the value of the resource is considered fresh (CoAp option: Max-Age). If not given, no fresh time is associated with the resource.value
is the default value of the resource. If not given, it is initialised to decimal 0.etag
is a Boolean argument that enables/disables entity tag calculation (CoAp option: ETag). By default it is turned off.Media-type argument is one of the standard defined values that is available via CoAp module’s constants.
Entity tag calculation is a simple counter increment between value 1-65535 with overflow, it doesn’t include the value 0. It is incremented each time and the value of the resource is changed.
Removes the resource defined by the uri
argument.
uri
is the full path of the resource to be removed.Returns with the resource defined by uri
argument.
uri
is the full path of the resource to be returned.Must be called when a packet is received on the socket assigned to the CoAp module. This function passes on the incoming request, whilst also composing and sending out the response if needed.
Registers a callback function which will be called when a remote CoAp Server responses to the local CoAp client’s request.
callback
is the callback to be registered. It must have the following arguments:code
is the response code from the received messageid_param
is the transaction ID of the received message. This can be used to match together requests and the response for it.type_param
is the type flag from the received messagetoken
is the token field from the received messagepayload
is the payload of the received messageCreates and sends a request to a CoAp server.
uri_host
is the IP address of the server, included in the message as an “URI-HOST” optionmethod
is the method to be sent to the server, can be: Coap.REQUEST_GET
, Coap.REQUEST_PUT
, Coap.REQUEST_POST
, Coap.REQUEST_DELETE
uri_port
is the port of the server, included in the message as an “URI-PORT” option. By default it is 5683uri_path
is the full path of the resource in the server, included in the message as an “URI-PATH” option. If nothing is given the request will not have URI-PATH option.content_format
is the Content-Format option of the request, can be: Coap.MEDIATYPE_TEXT_PLAIN
, Coap.MEDIATYPE_APP_LINK_FORMAT
, Coap.MEDIATYPE_APP_XML
, Coap.MEDIATYPE_APP_OCTET_STREAM
, Coap.MEDIATYPE_APP_RDF_XML
, Coap.MEDIATYPE_APP_EXI
, Coap.MEDIATYPE_APP_JSON
, Coap.MEDIATYPE_APP_CBOR
. If nothing is given the request will not have Content-Format option.payload
is the payload of the request. If nothing is given the request will not have payload.token
is the token field of the request. If nothing is given the request will not have token field.include_options
decides whether put any options (including the ones above) into the message or not. It can be used to send special requests to servers accepting CoAp formed requests without options, e.g. to a Dish Telemetry server. By default, the options are included.The resource class represents a resource in the scope of the CoAp module when acting as a server. A new resource can only be created with the Coap.add_resource
function.
Adds a new attribute to the resource. Attributes are used to explain the resource during service discovery.
name
is the name of the resource.value
is the value of the resource.During service discovery, GET request to “.well-know/core”, the attributes are returned with the relevant values. E.g. using the “libcoap’s” command line coap-client to fetch the resource from our server:
coap-client -m get coap://<Coap-Server’s address>/.well-known/core
< /resource2>,< /resource1>;ct=0;title=resource1
Updates or fetches the value of the resource.
value
is the new value to update the current value with.
If the method is called without a parameter, the current value is returned.To enable or disable a specific operation (GET, PUT, POST, DELETE) on the resource.
operation
is the operation to enable/disable, can be ORED of the followings: Coap.REQUEST_GET
, Coap.REQUEST_PUT
, Coap.REQUEST_POST
, Coap.REQUEST_DELETE
enable
is Boolean parameter that enables/disables the operations specified by operation
During a GET request, only the first occurrence of an ETAG or Accept option is passed on and interpreted; others of the same type are dropped (if any).
During a PUT request, only the first occurrence of an If-Match option is passed on and interpreted; others of the same type are dropped (if any).
Due to limitations of the underlying ESP-IDF/libcoap library, new resources cannot be added via PUT or POST requests.
Coap.MEDIATYPE_TEXT_PLAIN
, Coap.MEDIATYPE_APP_LINK_FORMAT
, Coap.MEDIATYPE_APP_XML
, Coap.MEDIATYPE_APP_OCTET_STREAM
, Coap.MEDIATYPE_APP_RDF_XML
, Coap.MEDIATYPE_APP_EXI
, Coap.MEDIATYPE_APP_JSON
, Coap.MEDIATYPE_APP_CBOR
Coap.REQUEST_GET
, Coap.REQUEST_PUT
, Coap.REQUEST_POST
, Coap.REQUEST_DELETE