Network Programming in .NET: September, 2006

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September 25

Java Midlet for .NET web services

Ever wonder how they make Java games for mobile phones, and ever wondered how to make something more useful on them than a Game. I was curious, and thought about writing an app that can use a webservice from a mobile phone (mine's a Sanyo S750i). To dispell the myth that networking from phones is expensive. I checked my credit before and using this code, and it only cost me 2p. No Lie!.

To cut to the chase, you can download the source code from http://www.freebiesms.com/javasms.zip and the JAD file (for a mobile phone) at http://www.freebiesms.com/sms.jad

First off, you'll need to download the Java Micro Edition (v5), get the bundle with the NetBeans IDE. You'll also need to download the Netbeans mobility pack v5. This makes it easy to develop mobile applications (although the GUI designer is rubbish).

- ok cut short. need to go to work. Check out the code to see how I did it! :)

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September 20

Visitor Tracker in ASP.NET

Visitor trackers aren't new, and even novice HTML coders can place a free tracker in their webpage, but there comes a point when

you outgrow what's available free, and you really need to get hold of the raw data behind your tracker.

Recording data for every visitor to the site may be out of the question, as you end up filling your database with too much archival data. Generally a tracker will keep detailed information about the last day's traffic, then aggregated information for archival material. For example, it might be of interest to view which websites the last 20 visitors came from, but just a count of how many people came to the site last march might be sufficient.

I therefore created two tables in my database, RecentVisitors and AggregatedVisitors. With a trigger set up between the two, to automatically populate the AggregatedVisitors table based on new inserts into the RecentVisitors table, thus:

CREATE TRIGGER trigger_RecentVisitors
ON RecentVisitors
FOR INSERT
AS
BEGIN
-- note this will track hits not unique visitors.

declare @websiteID int

select top 1 @websiteID = websiteid from inserted

declare @VisitorsToday int
select @VisitorsToday = count(*) from RecentVisitors
where dateDiff(day,Date,getdate())=0
and websiteId=@websiteID

delete from AggregatedVisitors where
websiteID = @websiteID
and
Datediff(day,date,getDate())=0

insert into AggregatedVisitors (Number,websiteID)
values (@VisitorsToday,@websiteID)

delete from recentVisitors where dateDiff(day,Date,getdate())>1

END

I then, put together some javascript to load a hidden image, which would execute an insert into RecentVisitors

<img name="Tracker" style="display:none">
<script language="javascript">
var WebsiteID = 1;
var Tracker = window.document.images["Tracker"];
Tracker.src = "default.aspx?WebsiteId=" + WebsiteID + "&Referrer=" + escape(document.referrer);
</script>

To return a 1px x 1px image from asp.net is really easy, and combined with an insert into the database, I came up with:

if (Session["FirstTime"]==null)
{
   string strReferrer = Request.QueryString["Referrer"].ToString();
   int intWebsiteID = Convert.ToInt32(Request.QueryString["WebsiteID"]);
   string strSQL = "insert into RecentVisitors (IP,Referrer,websiteId) values (";
   strSQL += "'" + Request.ServerVariables["REMOTE_ADDR"] + "',";
   strSQL += "'" + strReferrer.Replace("'","''") + "',";
   strSQL += intWebsiteID + ")";
   base.ExecuteNonQuery(strSQL);
   Session["FirstTime"]=false;
}
Bitmap bmpCanvas = new Bitmap(1,1);
Response.ContentType = "image/gif";
bmpCanvas.Save(Response.OutputStream,ImageFormat.Gif);

ExcecuteNonQuery is a function I wrote to run a statement against the database, and is outside the scope of this blog.

Then, to view this data in a meaningful way, I created a page with two dataGrids, dgRecentVisitors and dgAggregatedVisitors, which used the following SQL to display their results:

select top 20 rv.id,referrer,date from recentvisitors rv
join websites w on w.id = rv.websiteid
where charindex(w.websiteaddress,rv.referrer)=0
order by date desc

and

select * from aggregatedVisitors order by date desc.

and, that suffices for a tracker for my purposes, and I have access to the raw data, should I need to run queries to work out sales conversion rates etc. The only downfall is that it does not correctly measure visitors rather than hits, but that's work for another day.

Njoy.

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