Basic Service Sample

This sample demonstrates how to register a DXL service to receive dxlclient.message.Request messages and send dxlclient.message.Response messages back to an invoking dxlclient.client.DxlClient.

Prior to running this sample make sure you have completed the samples configuration step (Samples Configuration).

To run this sample execute the sample\basic\service_example.py script as follows:

c:\dxlclient-python-sdk-5.6.0.4>python sample\basic\service_example.py

The output should appear similar to the following:

Service received request payload: ping
Client received response payload: pong

The code for the sample is broken into two main sections.

The first section is responsible for creating a dxlclient.callbacks.RequestCallback that will be invoked for a specific topic associated with the service. The callback will send back a dxlclient.message.Response message with a payload of pong for any dxlclient.message.Request messages that are received.

It then creates a dxlclient.service.ServiceRegistrationInfo instance and registers the request callback with it via the dxlclient.service.ServiceRegistrationInfo.add_topic() method.

Finally it registers the service with the fabric via the dxlclient.client.DxlClient.register_service_sync() method of the dxlclient.client.DxlClient.

#
# Register the service
#

# Create incoming request callback
class MyRequestCallback(RequestCallback):
    def on_request(self, request):
        # Extract information from request
        print("Service received request payload: " + request.payload.decode())
        # Create the response message
        res = Response(request)
        # Populate the response payload
        res.payload = "pong".encode()
        # Send the response
        client.send_response(res)

# Create service registration object
info = ServiceRegistrationInfo(client, "myService")

# Add a topic for the service to respond to
info.add_topic(SERVICE_TOPIC, MyRequestCallback())

# Register the service with the fabric (wait up to 10 seconds for registration to complete)
client.register_service_sync(info, 10)

The second section sends a dxlclient.message.Request message to the service that contains a payload of ping via the dxlclient.client.DxlClient.sync_request() method of the dxlclient.client.DxlClient.

The payloads of the dxlclient.message.Request and dxlclient.message.Response messages are printed.

#
# Invoke the service (send a request)
#

# Create the request message
req = Request(SERVICE_TOPIC)

# Populate the request payload
req.payload = "ping".encode()

# Send the request and wait for a response (synchronous)
res = client.sync_request(req)

# Extract information from the response (if an error did not occur)
if res.message_type != Message.MESSAGE_TYPE_ERROR:
    print("Client received response payload: " + res.payload.decode())