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Retrieving the data
We just pass on a SQL string thus:-
Private Sub cmdretrieve_Click()
lstData.Clear
Sbuff = "READSelect * from employees~"
tcpClient.SendData Sbuff
End Sub
That is the easy bit. We now have to
deal with the data, probably the most complex piece of code,
so we will break it down into bite-size chunks.
Private Sub Process_Records()
Dim WkErr
lRecs = CLng(Mid(Rbuff, 7, 6))
iFields = CInt(Mid(Rbuff, 14, 4))
WkBuff = Mid(Rbuff, 19, Len(Rbuff) -
18)
As we outlined earlier, the first 6
characters are the function return (READOK), followed
by 6 characters for the number of records, 4 characters
for the number of fields, and then the data. Accordingly,
we split out the buffer as above.
Data_Records = Split(WkBuff, "|")
Dim WkEmpno
Dim WkEmpFore
Dim WkEmpLast
Dim iFldNo As Integer
lstData.Visible = False
We separated our data with '|'
prior to sending it, so we again use the split function
to separate the data. 'Data_Records'
is now an array, containing all our data fields. The arrayupper
bound will equal our number of records multiplied by our
number of fields.
Our table contained employee number,
forename and surname, so our first record will be contained
in Data_Records(0), Data_Records(1)
and Data_Records(2).
When processing array data it is always
a challenge to find an algorithm to deal with it easily.
In this case, we can always say our loop starts at 0, and
ends at (number of fields - 1).
Our step value is the number of fields.
I have named the data items to (hopefully) make it a bit
clearer. This also makes it close to the way of addressing
fields in recordsets (rs.field(fldno).value).
So we just loop through the Data_Records
array, assigning our employee number, forneame and surname
as we go. (We could just as easily use the array values
directly, but I thought this way made it a bit clearer.
I am probably wrong, but what the hell!!). There may be
better ways of handling this - all suggestions welcome.
For iFldNo = 0 To (lRecs * iFields) -
1 _
Step iFields
WkEmpno = Data_Records(iFldNo)
WkEmpFore = Data_Records(iFldNo + 1)
WkEmpLast = Data_Records(iFldNo + 2)
lstData.AddItem WkEmpno & ":"
& _
WkEmpFore & " " & WkEmpLast
Next
Erase Data_Records
lstData.Visible = True
End Sub
Fire up the server and the client, connect
to the server, open the database, and hopefully you should
see on the server.
and on the client
Even taking into account the vagaries
of the winsock control, the results are fairly impressive.
This is just a simple example. Try it against your own databases,
with more data.
A full blown data server would cater
for multiple clients, allow SQL insert update and delete
statements, and probably run as a service, but this is just
a primer to fire the imagination (some hopes). This has
been tested 'wired' and wireless from an iPaq with no problems
whatsoever. The sample eVB project contains the code for
testing against the standard SQL Server test database 'pubs',
but the code is commented out. Just comment out the Access
statements and un-comment out the SQL Server statements
to test it (how would you like me to teach you to suck eggs,
Grandma?).
The test database and source code for
both projects are available for download.
In case you are wondering, the names from number 10 onwards,
are from the squad of Bolton
Wanderers (www.bwfc.co.uk).
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