[fpc-pascal] Serial to TCP gateway in FPC?

Bo Berglund bo.berglund at gmail.com
Sun Jul 2 13:33:00 CEST 2017

On Thu, 29 Jun 2017 10:39:05 +0200, Bo Berglund
<bo.berglund at gmail.com> wrote:

>For some unknown reason (so far) the remote side loses connection to
>the target system (no response after initially being able to talk to
>it). In fact this is reproducible 100%, the first handshake works and
>the system can be set to the new state, but on the next state change
>the 1-byte command is not responded to so the connection fails.

Just to close this thread...
I finally found the cause of the problem, which was a handshaking
timeout inside the PC control software.

The in-process state changes (1-byte commands) were supposed to be
acknowledged within 200 ms, and this is long enough for a physical
RS232 connection but too short when dealing with a TCP/IP translation
and transfer from Europe to USA and back.

When I added logging of the transmt and receive times of the data in
the relayer program I saw that the turn-around delays were about 300
ms normally, which is just a bit longer than what the software allowed
So we have to get someone revise the PC control software and increase
the timeout.

The Lazarus relaying program using FPC serial and Indy TIdTcpclient
components works just fine! Now also with millisecond logging.

Bo Berglund
Developer in Sweden

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