Hello dear forum users,

I have a task on my table to build up communication between S7-1500 PLC and PC over open user communication, using TCON, TSEND, TRCV and TDISCON. It is clear for myself how the communication works, but I am looking for best practice and advise how to build up state machine and in which order to communicate.

So, I have several messages that I have to send on it's own trigger. So, I was thinking about checking trigger of each message and if active send message over TSEND, when communication is established of course. TRCV would be active all the time when communication is established and listen for upcoming message, so when I receive the message I will check the header and if it is matching with header of sent message I would consider that message as response, but I am wondering if this is good approach, or should I send one message for example and wait for it's response, and only after received response send 2nd message, etc...

Have anybody of you done similar program already, that can share with me.

Have a look at the following library:
Libraries for Communication for SIMATIC Controllers

Focus especially on the Ethernet TCP template.

Also.. 
The newest V2.9 firmware update has some attributes that is a must have for better communication. Update your CPU to that update.

If your application allows for direct connection between the PLC and PC on a separate LAN adapter (on PC) and does not require packet sizes > ~1500 bytes and/or deterministic data exchange, you might consider looking into UDP (rather than TCP).

It's extremely simple to setup on the PLC end of things by comparison.  Reason is because you set up the UDP connection and start sending and enable receiving - blindly.

If there is no new data received within the expected amount of time from the PC, you may assume the PC is offline.

If, however, every byte sent or received is 100% required to be sent / received, TCP is definitely the way to go.

For simple data logging applications, UDP is often sufficient.

madnesssm

Hello dear forum users,

I have a task on my table to build up communication between S7-1500 PLC and PC over open user communication, using TCON, TSEND, TRCV and TDISCON. It is clear for myself how the communication works, but I am looking for best practice and advise how to build up state machine and in which order to communicate.

So, I have several messages that I have to send on it's own trigger. So, I was thinking about checking trigger of each message and if active send message over TSEND, when communication is established of course. TRCV would be active all the time when communication is established and listen for upcoming message, so when I receive the message I will check the header and if it is matching with header of sent message I would consider that message as response, but I am wondering if this is good approach, or should I send one message for example and wait for it's response, and only after received response send 2nd message, etc...

Have anybody of you done similar program already, that can share with me.

Hi there,

Thank you for heads up.

Yes, each and every byte has to sent/received. As on the oposite side is the Pc with 3rd party application the only way for vommunication that they support is this kind. So, it is required to sent everything as character, so my package will bi array of characters for sending and receiving, always same length.

So, I have created project in TIA portal eith two PLCs and communication works fine, but next step would be to download on real PLC and test it with my PC. As PLC will be passive and PC has to be active, what may I use on PC to establish communication as active partner and track the messages received? 

Using Putty (https://putty.org) is an option for having some PC application to test with.

Someone has published some Python code on this forum too. Have a look, but do not expect any support on it. [ Interface in Python => PLC S7-1200 ]