Ararat Synapse RecvString() question

[rainer]

Hello. 
I am not sure where ask this question, so I try here.

I am working on a little daemon (server), written in FreePascal on|for Linux.   It will communicate with IoT clients through TCP/IP. 
My problem is this extremely unreliable NB-IoT.  Sometimes Round-Trip-Times of 3-5 seconds, sometimes connection loss, ... 

I wrote a function to transmit a data packet. It sends a string, then it awaits the confirmation (a string with 'ACK'+<CRLF>). I configured a very long timeout of 15s for receiving a response (because of this sometimes long delays).

Code: Pascal  [Select][+][-]

1. // Send data
2.   function SendDataBlock(DataBlock: string): boolean;
3.   var  s: string;
4.   begin
5.     ASocket.SendString(DataBlock+CRLF);   // Send Data
6.     s:=ASocket.RecvString(timeout_rcv);   // Await respoonse
7.     SendDataBlock:=pos('Ok',s)>0;    
8.   end;
9.  

This function works fine, as long something is received.  But it rises an Exception when Synapse reaches the timeout (line 6).

Is there a simple way to make RecvString return an empty string on timeout, or to detect and trigger on timeout?


I spent lots of time on finding any useful documentation, code examples, etc., but I had no success.    Is there any "code collection" available as downloadable PDF, showing how to use Synapse?  Need to say, I do not use Lazarus.  I use only FreePascal.  If somebody wants to see the complete code for better understanding, this is possible on request.

[paweld]

You can disable exception throwing by synapse. Add the following code after creating TBlockSocket:

Code: Pascal  [Select][+][-]

1. ASocket.RaiseExcept := False;