Re: How do I design this application ? (remote server procedures,
etc.)
Me wrote:
I need to build a remote weatherstation that I can view from a browser
anywhere on the web.
The weatherstation instrument has an RS232 port. I can communicate with
it using python or java (rxtx).
The weatherstation instrument is going to sit at the weatherstation
location where it will be connected to a server running apache.
I need to design a system that gets served from the server so that a user
with a browser that connects to the server can see the data from the
weatherstation and interact with it.
I am fluent with java, python and c/c++. But I've never built anything
to run in a browser or that was served from an html server.
How does one "connect" a button press on the served page back to an
action on the server ? ie If I press button "get data" on the served page
in the browser connected to the server, how does that result in an action
on the server, ie call the routine to get the data from the weather
instrument.
How does one "connect" a field on the served page back to changing data
on the weather instrument ? ie: windspeed might change ever 10 seconds.
I can make a program on the server get a new windspeed reading every 10
seconds. But once I have the reading, how do I update the windspeed
field on the served page ?
Could someone recommend a good book that covers these topics in detail ?
Thanks
There are a lot of ways to go at this. I'm really only familiar with
some of the simple approaches. So let me tell you a little about a
system I have running currently that uses applets, apache and Java
applications. It's a project I did for a Red Cross chapter. They
wanted to display some data on a video screen in their emergency
operations center and they wanted to enter that data through a web
browser (I would have preferred an application but the client is paying
:-). I have a computer running a Java application that communicates
with the Java applets that are used to modify the stored data. The
applets are simple field based editors. That application also creates a
screen for display in the EOC. In addition that application can be run
remotely for display purposes only by accessing the data files from the
primary host via HTTP. In addition I create an HTTP file that has some
of the data on it for access from the outside world through a password
protected web page. There is also an HTTP log system that creates an
easily accessed hourly report of all the data in the system. This is
just another task running in the host. This project even has a perl
script that takes data from a form and creates HTML for it's own data
entry and for display in the EOC.
None of it uses any of the tricky new fangled stuff like AJAX or
servelets or whatever. Not because I disdain it but because I don't
really understand it all that well :-). And I'm a fan of simple too.
So I think in your case, running a Java app locally to deal with the
weather station and create pretty HTML for your clients might just be
the simple way to go. If you need to be interactive with the client
then maybe something more sophisticated will be required.
--
Knute Johnson
email s/nospam/knute2009/
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