Reading delimited packets with Indy TIdTCPServer in C++Builder - c++builder

Question

I have a microprocessor device that wants to connect to a TCP server and then send a token each time its input state changes. The tokens are in the form "AS9=0;" with no CR or LF. Each token is sent in one packet identified with a length of 6. For my project to work properly, I want to allow the connection to open, receive the data, and use it without waiting for another packed or closing the connection.
The socket component set that comes with C++Builder is Indy 10. It represents an astonishing amount of work. However, all that work is in Pascal, not much use to me. It would be generous to say that the documentation is difficult. Ideally, I would like to read the data on a packet per packet basis. I can identify no means to do this. I have tried the AllData() method. Although it works, it waits until the connection is closed to read out the data. This is not usable for me. I have also tried the ReadLn() method. It reads out the data once it encounters a LF. It too is useless as my data contains no LFs.
So far, my code looks like this:
void __fastcall TForm1::IdTCPServer1Execute(TIdContext *AContext)
{
UnicodeString mystring;
RichEdit1->Lines->Add(" * ");
mystring = AContext->Connection->IOHandler->AllData();
RichEdit1->Lines->Add(mystring + " *** ");
}
//-----------------------------------
void __fastcall TForm1::IdTCPServer1Disconnect(TIdContext *AContext)
{
RichEdit1->Lines->Add("Disconnected. . . \r\n");
}
//--------------------------------------
void __fastcall TForm1::IdTCPServer1Connect(TIdContext *AContext)
{
RichEdit1->Lines->Add("Connected. . . \r\n");
}
//---------------------------------------
As I mentioned, the above code will show everything, but only once the connection is closed. Given all of this, I have two questions. First, how can I grab data as soon as the packet comes in? Second, for the ReadLn(), how can I change the line delimiter from a LF to a ";"?

Answer 1

If you look at the declaration of TIdIOHandler::ReadLn(), you will see that it has an optional ATerminator parameter:
String __fastcall ReadLn(_di_IIdTextEncoding AByteEncoding = NULL);
String __fastcall ReadLn(String ATerminator, _di_IIdTextEncoding AByteEncoding);
String __fastcall ReadLn(String ATerminator, int ATimeout = IdTimeoutDefault, int AMaxLineLength = -1, _di_IIdTextEncoding AByteEncoding = NULL);
If you don’t specify a terminator, the default is LF (which includes CRLF). You can specify a different terminator as desired, eg:
void __fastcall TForm1::IdTCPServer1Execute(TIdContext *AContext)
{
...
String mystring = AContext->Connection->IOHandler->ReadLn(_D(";"));
...
}
On a separate note, TIdTCPServer is a multi-threaded component. Its events are fired in the context of worker threads. As such, you MUST synchronize with the main UI thread when accessing UI controls, eg:
void __fastcall TForm1::AddLine(const String &S)
{
#if defined(__clang__)
TThread::Synchronize(nullptr, [&, this](){ RichEdit1->Lines->Add(S); });
#else
struct TAddLineSync
{
String Line;
TAddLineSync(const String &ALine) : Line(ALine) {}
void __fastcall AddLine() { Form1->RichEdit1->Lines->Add(Line); }
};
TAddLineSync sync(S);
TThread::Synchronize(NULL, &sync.AddLine);
#endif
}
//-----------------------------------
void __fastcall TForm1::IdTCPServer1Execute(TIdContext *AContext)
{
AddLine(_D(" * "));
String mystring = AContext->Connection->IOHandler->ReadLn(_D(";"));
AddLine(mystring + _D(" *** "));
}
//-----------------------------------
void __fastcall TForm1::IdTCPServer1Disconnect(TIdContext *AContext)
{
AddLine(_D("Disconnected. . . \r\n"));
}
//--------------------------------------
void __fastcall TForm1::IdTCPServer1Connect(TIdContext *AContext)
{
AddLine(_D("Connected. . . \r\n"));
}
//---------------------------------------