ASTA Vision

ASTA Vision

ASTA Messaging

One of ASTA’s design goals was “To provide a Messaging Layer that can be used by Database Developers that are NOT socket programmers”.

Both the AstaServerSocket and AstaClientSocket have easy to use messaging calls. You can send a string or a stream with SendCodedMessage or SendCodedStream. The AstaServerSocket takes an extra argument of ClientSocket:TcustomWinSocket but otherwise the calls are the same.

Here is the way the ASTAClientSocket can be used:

Procedure SendCodedMessage(Msgid:Integer;Msg:String);

AstaClientSocket1.SendCodedMessage(1000,'Hello World');

procedure SendCodedStream(MsgID: Integer; MS: TMemoryStream);

Then on the Server you would just code the AstaserverSocket.OnCodedMessage

like this:

procedure TForm1.AstaServerSocket1CodedMessage(Sender: TObject;

ClientSocket: TCustomWinSocket; MsgID: Integer; Msg: String);

begin

Case Msgid of:

   1000:AstaServerSocket1.SendCodedMessage(ClientSocket,1001,'Hello back to

   you!');

end;

end;

When we built ASTA there were times of course that we wanted to send other

kinds of data than strings and streams so we created the TAstaParamList. The TAstaParamList is just like a TParamList that you are familiar with on the TQuery component but it is fully streamable. It also can contain DataSets, any kind of binaries and even other ParamLists.

So once we created the TAstaParamList and the call

Procedure SendCodedParamList(Msgid:Integer;Params:TAstaParamList);

we pretty much could transport anything back and forth between servers and

clients (and client to client also) easily.

But you say, in the above examples we send in one place and receive in an event and you told us that you saved us from that.

Astaclientsockets have a call of SendGetCodedParamList which sends a

TastaParamList and also waits until the server sends back a response. This

allows to write procedural code rather than event driven code.

Var

P1,P2:TAstaParamlist;

begin

P1 := TastaParamList.Create;

try

p1.FastAdd('Hello World');

p1.fastAdd(Now);

p1.FastAdd(4.333);

p2:=AstaClientsocket1.SendGetcodedParamList(1010,p1);

//do something with the P2 Paramlist that is returned from the function

result

    finally

   p1.free;

   p2.free;

end;

end;

ASTA users have thought of all kinds of ways to use ASTA messaging from taking

fairly static queries and executing and compressing them on ASTA servers to be

sent out using ASTA messaging, to controlling remote servers, to getting back

performance information form servers, to sending faxes.

Once you have a middle tier there is a complete world that opens up of new

possibilities.

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