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Server Socket Queues

I need to write an application to act as an interface between several cash register systems (all the same type) and a customer loyalty system.

I can write procedures to pick up data from the customer loyalty system without any problems.

I have written a procedure using TServerSocket to receive packets from a socket client and it works OK most of the time.

The problems I am having are:
1. There seem to be many different errors I need to trap and handle. I don’t know what these all are or how to handle them. e.g. Socket Connection errors.

2. I am using a procedure called: TMain_Form.CashRegisters_ServerClientRead(Sender: Tobject; Socket: TCustomWinSocket);. When I receive only one packet at a time, it works OK. If I receive a second packet while this procedure is processing the first packet, it stops processing the first packet until the latest packet has been handled.
I want the program to process packets on a first-in first-served basis.

I am fairly new to Delphi programming and have no experience (until a few days ago) using sockets. I don’t have a lot of time to finish this project.

My preference would be to find a component that will handle the errors and queueing for me.

Are there any components available to do this? I would prefer freeware or shareware so I can try before I buy.

akb

Asked: 2002-04-15

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1 Solution

LVL 12

Lee_NoverCommented: 2002-04-16

>>If I receive a second packet
while this procedure is processing the first packet, it stops processing the first packet until the
latest packet has been handled.<<

so you're using non-blocking sockets
make the server thread-blocking

LVL 13

akbAuthor Commented: 2002-04-16

Thanks Lee. That may help a little, but it doesn't overcome my first problem and lack of experience.

I'd really like to find an add-on that will handle the socket for me.

LVL 14

DragonSlayerCommented: 2002-04-16

Have you tried the Indy components? (they come with Delphi6 and can also be downloaded from http://www.nevrona.com/indy/)

Check out their examples in using threads... there you will see how they create new threads to handle each request simultaneously.

HTH
DragonSlayer.

LVL 13

akbAuthor Commented: 2002-04-16

Thanks DragonSlayer. The Indy components look like they may be useful. I have downloaded them and will try them out shortly.

LVL 2

freshman3kCommented: 2002-04-17

Hello!

This component is what you need:
http://overbyte.alexid.fr/frame_index.html

Good Luck!

LVL 13

akbAuthor Commented: 2002-04-17

Thanks freshman3k. I'll take a look at these components as well.

LVL 12

Lee_NoverCommented: 2002-04-17

if you're going to use indy then take a look at some of my helper functions @ http://lee.nover.has.his.evilside.org/isapi/pas2html.dll/pas2html?File=/delphi/MiscFiles/vn_common/

LVL 13

akbAuthor Commented: 2002-04-17

Thanks Lee Nover.

LVL 13

akbAuthor Commented: 2002-04-17

Thanks Lee Nover.

LVL 13

akbAuthor Commented: 2002-04-17

I am trying out the Indy components. I have replaced my old TServerSocket with the Indy TldTCPServer. And I'm using the OnExecute event instead of the OnClientRead event.

The problem is, I am also caling Apollo database components to look up data in my old DBF files. As soon as I call the Apollo Seek component, I get an error box about 30 times and no returned data. The error is:

Data Driver Error
Error:3200
Invalid work area

I am happy to increase the points for help on this problem.

LVL 12

Lee_NoverCommented: 2002-04-18

this kinda doesn't fit into the current topic
but still .. I think it's coz the OnExecute event of the server is in the context of the AThread param
so you should do smth like: AThread.Synchronize(DoApolloStuff);

LVL 13

akbAuthor Commented: 2002-04-18

Thanks Lee. I know this is off the thread, but I am willing to pay points for help.

I am calling my procedure with:
AThread.Synchronize(GetMemberDetails(MemberID));

When I compile I get:
[Error] main.pas(866): Incompatible types: 'TThreadMethod' and 'procedure, untyped pointer or untyped parameter'

Also, can I make GetMemberDetals a function and return a result from it?

LVL 12

Lee_NoverCommented: 2002-04-18

no you can't
make it a parameterless procedural handler

make one global variable - MemberID (to the owning object)
then in the GetMemberDetails procedure handle the necessary things

an example from one of my apps :

procedure TPreviewF.tcpCommExecute(AThread: TIdPeerThread);
var Header: TCommHeader;
begin
if not GetHeader(AThread.Connection, Header) then
Exit;

// LastCL and LastHeader are global variables
LastCL:=TCrossLink(AThread.Data);
LastHeader:=Header;
AThread.Synchronize(DoCommExecute);
end;

procedure TPreviewF.DoCommExecute;
var CurrThread: TidPeerThread;
Header: TCommHeader;
begin
// here I assign the global variables to the procedures local variables
CurrThread:=LastCL.AThread;
Header:=LastHeader;
HandleRequest(CurrThread.Connection, Header);
end;

LVL 13

akbAuthor Commented: 2002-04-18

Thank you, Thank you, Thank you, Thank you, Thank you!!!

I will give the points for this question to DragonSlayer as he answered the original question and I am using the Indy components.

I will post a new question in order to give you points, Lee Nover. What do you consider to be a reasonable number for your help?

PS. is Lee Nover your real name or is it a made up name like Ben Dover or Ilene Dover?

LVL 13

akbAuthor Commented: 2002-04-21

Lee Nover, please see above comment

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