Many thanks for the answer!!!
I am sorry but the MS-DOS version of this software was discontinued in the year 1998 or 99. There is no DOS driver available anymore. The Send / Receive interface you found is the C interface for the nowadays available drivers as part of the SOFTNET S7 or SOFTNET S7-Lean packages for Windows.
If I correctly have understood you, free libraries for an exchange with controllers S7<->PC (TCP/IP) do not exist?
There you have the Send / Receive interface also in C. If you want to use Fetch / Write, as Service on the Send / Receive interface you may handle the Appendix as mentioned in the Document you posted first.
Thanks, but I cannot understand - CPU 315-2 PN/DP supports an exchange on S5 protocol which is described in "SIMATIC NET NCM for Industrial Ethernet" C "Linking to Other Systems with FETCH/WRITE" and "SEND/RECEIVE Programming Interface" 2 "Communication with SIMATIC S5 Programmable Controllers"???
But be aware the OPC Server extension of the Fetch / Write is pretty fast, maybe even faster than your Dos Window app.
I worked with several OPC-servers, unfortunately, experience not always was positive. Therefore, if there is a possibility I try to write the driver of an exchange with the controller (for me a wide experience of a spelling of drivers with controllers). But in case to write the exchange driver it is impossible or very long, I use an OPC-server.
And please understand me correctly, I do not think that your OPC-server bad, simply I should ensure functioning a SCADA&OPC-server together and to me to write the driver easier and to be responsible for its working capacity.
Needless to say that Send / Receive is not the S7-Protocol... just to remember.
Yes, it S5 the protocol or as it name on another: FETCH/WRITE, and sometimes Send/Receive. To me not important what protocol, the main thing that by means of it I could receive values of parametres and control them.