Dear experts,

I did some TCP/IP communication between my s7-1214C DC/DC/DC and a third-part software to check the transmission data.

I checked in a network sniffer that the data part of the TCP packet, sent by the s7-1200 PLC, has a fixed "header" in the beggining - 2 bytes to be exactly, "FE" and "28". (see attached picture).

 These "FE" and "28" are regard to the total lenght and actual data size, but the third-part software is not expecting these kind of "header".

Question: is it possible for the PLC, with the T_SEND_C function, not to send these information in the beggning of the data packet?

Thanks in advance.

Hi Kaulquappe,

Thanks for the fast answer

I actually created a DB with a string area that contais the data to be sent.

In the TSEND_C function I pointed to this area in the DB, as you can see in the attached picture.

Is there other way to point to the correct segment of the string? In Step7 I was abble to use some kind of P#DBx.DBXx.x, I also tried this in TIA, without success..

If you could help me to find the information in online help, I'd appreciate.

Regards!

Hello guys,

this is VARIANT data type in this case so look at this in TSEND_C help in TIA:

You can find additional information on valid data types under "Overview of the valid data types".

Click on this link in TIA help as I said.

Hi guys,

Didn't understand where I should use a variant type of data..

I'll try to work with an array of char to see if it works..

Hello Duris_I!

Thanks for your answer.

By any chance do you have an example of how to address my array of char using variants, in TIA?

Regards,

SalatiM

Hello Duris_I!

Thanks for your answer.

By any chance do you have an example of how to address my array of char using variants, in TIA?

Regards,

 hi SalatiM,

I found a FAQ for you:

How in STEP 7 (TIA Portal) V11 do you program the data type "VARIANT" for indirect addressing for the S7-1200?

hope this helps, 

regards,

A string is indeed prefixed by 2 bytes and that's exactly what is send. If you don' like that construct your own send buffer (e.g. byte/char array), copy the wanted string chars to it and use that to send.

You can use the Strg_TO_Chars instr.

Hello all,

Did the tests with variant addressing of the string data type, and the result was the same, as enof said, these 2 bytes are a prefixed index.

The only way to solve was to address the data in TSEND_C function using a buffer as a array of char.

Thanks all of you so much for the help.

Best regards.