Running the Python Client and Server¶
We now have all of the pieces needed for a simple working RPC example. The instructions on this page assume you have already followed the directives for building and installing the HelloRPC service contract in Python as outlined on the Compiling and Installing the Library page earlier in the tutorial. If you have not done this, please do so now before trying the steps below.
Python Client and Local Python Server¶
To run the HelloRPC example with a Python client against a local Python Server do the following:
Step 1: Move to the location where you saved the Python server you wrote earlier in the tutorial. Alternately, move to the HelloRPC directory within your local Datawire Connect git repository. If you use the default location, do the following: cd ~/quark/examples/helloRPC
Step 2: Run the server by executing the following command: python pyserver.py. This will result in a blocking wait state - there is no direct output to stdout from the Python server.
Step 3: Open a second terminal window
Step 4: Move to the location where you saved the Python client you wrote earlier in the tutorial. Alternately, move to the HelloRPC directory within your local Datawire Connect git repository. If you use the default location, do the following: cd ~/quark/examples/helloRPC
Note: If you use the supplied client file from the GitHub repository (pyclient.py), you must edit it to point to the local helloRPC server instead of the helloRPC server in the Datawire cloud. To do this, change the URL passed when instantiating the client object from http://hello.datawire.io to http://127.0.0.1:8910/hello. For more information, refer to the client instantiation section of the walkthrough.
Step 5: Run the client by executing the following command: python pyclient.py
You should see the following in your terminal window (stdout):
Request says 'Hello from Python!'
Response says u'Responding to [Hello from Python!] from Python'
The u in the response text indicates that the response is in Unicode. The first line is defined and printed by these two lines in the Python client we wrote:
request.text = "Hello from Python!"
print "Request says %r" % request.text
The second line is printed by this line in the Python client we wrote:
print "Response says %r" % response.result
The value of response.result is set in the server inside the implementation definition (HelloImpl class) using this line:
res.result = "Responding to [%s] from Python" % request.text
[[JMK note that the %r in the client print lines should likely be %s and the %s in the server code should likely be %s. See issue #85]]
That’s it! You should now understand how to define clients and servers to use the basic RPC interaction pattern defined in Datawire Connect and have seen those clients and servers in action in Python.
Using the Python Client Against the Cloud¶
One of the first things we did in this walkthrough was use the example Python client file against the Datawire cloud and see it respond to the client requests. You can do exactly the same thing with the Python client you wrote by changing the server URL supplied when instantiating the client object. Just swap out http://hello.datawire.io for http://127.0.0.1:8910/hello and run the client again. This time it should tell you that the response is coming from the Datawire cloud.