I’m looking for a best-practice for the following scenario:
A Mobile Device (iOS) sends its (Sensor-)Data to another device (iPad, Laptop, PC, whatever) over the Internet in realtime.
Sure, I need a web service but as far as my understanding is, a webservice gets “called” and returns Data or takes Data. But I require a constant exchange of sensor data between two devices in nearly realtime. I’m looking to implement something like a Multiplayer Online Game, how do they do such a thing? Or the Glympse service?
The way I’d approach it is to create a “server” out there on the net, that would run some application (like a CGI script) to collect the data (store it, in maybe a database) – then allow the remote device to query it.
This means that every device has a “well-known service” which they are connecting to – potentially “logging into” – and selecting the data from.
For example, each “client” could push their “vessel name” and GPS location. The CGI script on the server would just put these in a MySQL database – as simple table containing “Vessel name” and “Location”.
Alternativiley, clients could query and “pull” GPS locations for a specific vessel name. As simple CGI script that would take “Vesel Name” as a value, and send a MySQL query to the database to return the “Location”. It could send the location (and vessel name) back in XML format.
The iPhone client could user NSXMLParser – or even a JavaScript “AJAX” client could use it’s own inherent XML parsing capabilites to send a request for one (or more) vessels, and receive the results.
What you don’t want to do is to have each client have to speak directly to each other client. This will get you into trouble with firewall rules, and mess up when you try to scale many-to-many communications.