Tuesday, December 22, 2009

Example Phy2Phy Interaction web service

So here is an example of a Phy2Phy interaction web service: http://phy-to-phy.appspot.com

The concept is that the web service is a database of devices and their states. The main URL is a "human interface" that displays the entire database and lets you enter a device name and it's current state.

The "computer interface" is at http://phy-to-phy.appspot.com/update. You perform an HTTP GET, with a URL of the form:

http://phy-to-phy.appspot.com/update?q=[device to query]&d=[device to set state]&s=[state]

So for example, if I want to set the state of device "PIR" to "1" and at the same time query the state of "SolarCell", I'd send:


And the response would be something like:


Indicating that the device "SolarCell" has a state "1.8". When calling the service, you can leave out the "q=" query if you just want to set a device to a state, or leave out the "d=" and "s=" if you just want to query for a device state.

So for example, on an Arduino you would attach an Xport set to connect using TCP to IP address (phy-to-phy.appspot.com), port 80, and using the NewSoftSerial library, your code snippet to set "PIR" to "1" would look like:

NewSoftSerial xport(3,2);


xport.print("GET /update?d=PIR&s=1 HTTP/1.1\r\nHost: phy-to-phy.appspot.com\r\n\r\n");

On a Make Controller, you would send the same string using SocketWrite.

In a few weeks, I will put up some code that also reads queries back from the phy2phy intermediation web service as well.

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