In a transactional system, it is required to connect as a client to a Server of another system and respond to request messages from the server.
How can the OnExecute event be emulated with Indy's TIDTCPClient component in Delphi?
Thank you
In a transactional system, it is required to connect as a client to a Server of another system and respond to request messages from the server.
How can the OnExecute event be emulated with Indy's TIDTCPClient component in Delphi?
Thank you
There are several aspects that the component event covers , and in my opinion, you are not specific enough about which of those behaviors you want to emulate .
OnExecute
TidTCPServer
I will assume that what you are looking for is to automatically detect if there is data to read and to launch an event that can read this data, so my answer covers this aspect in the simplest way I can think of.
Initial considerations
Before developing my answer, I will limit once that the component
TidTCPServer
is a MultiThreaded component, that the OnExecute event occurs in the context of a secondary thread, and therefore its activities are carried out in the background (unless the opposite is programmed). I am not trying to repeat this behavior (for simplicity of the solution). Also, being a server, there can be severalOnExecute
running at the same time, one for each connected client, this would be impossible to replicate in aTidTCPClient
, since the client can establish a single connection to a single server.Simple solution on the main thread
That said, the easy solution would be to establish the connection and from there constantly check if there is data to read from the server. We can do this, for example, with a TTimer. Whenever there is data, we react to that event appropriately and then periodically continue to wait for more data.
I have prepared and executed an example, where the client component has a ReadTimeout of 100 ms. to avoid that the application remains stopped for a long time waiting for information. The server sends commands , which are text strings terminated in CRLF, with a greeting, a counter, and the time the message was sent. For each command the client adds the content to a memo prefixing the time the command was received. The timer runs every second.
The relevant client code is this:
At run time, it looks like this:
other possibilities
That said, you could also perform, analogous to what the Indy server component already does, all of this action in a secondary thread. In fact, thinking object-oriented , you could make a component that internally has a TidTCPClient and that already has the functionality to perform all these actions in a secondary thread, and fire an event to the UI every time there is new data (which it's basically what happens behind the scenes of OnExecute ).
It is among, perhaps, many other solution alternatives, which are outside the scope of this short answer.