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Can PLC parse messages using CR+LF?

Created by: vbardelli at: 3/11/2010 9:12 AM (1 Replies)

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3/11/2010 9:12 AM	Rate (0)
vbardelli Posts: 2 Rating: (0)	Thank you very much for your answer J_Bell. :) Infact, finally, we use passive mode with a fixed local IP address and a localport that we choose. In the PLC we don't choose any remote IP address and remote port (this means that PLC accept connection from any IP addresses and ports). We choose the passive mode. I use ethernet and TCP/IP only to connect the Supervisor PC to PLC. In the PC I have another ethernet board to connect to intranet, so it's not a problem. At the PC sidewe choose an IP address (for the PC) on the same net of the PLC (if the PLC was 192.168.0.1, the PC was, for example, 192.168.0.10). Then my program try to connect to 192.168.0.1 at the same port indicated in the local port at the PLC side. It seems to work. I have only toinvertbytes for int and real at the PLC side, whenI receive messange and when I sendthe answer, but this is not a problem. Good. Now I have another problem. In my program I have two threads that talk to PLC over ethernet.One that asks the machine status every second, and another one that sends the move commands to the machine. So the TCP/IP can sendtwo messages together. I have an header (CR+LF) and a footer (CR+LF) to separate messages, but I think that FC_RECV in the PLC is able only to receive a particular message size (one message). So, what happen in this condition? The CP 343 Lean is not able to queue the messages? It seem that it overwrites the first message with the second one, so, if the first message was the status request is not a problem, but if the first one was the move command, I have lost this message! Is that correct?Is there any solution about this problem? Can PLC parse messages using CR+LF? Any help isvery appreciated... Have a niceday, Valerio
vbardelli Posts: 2 Rating: (0)	Last edited by: O_Moderator at: 3/12/2010 9:37 AM new subject after splitting from /tf/WW/en/Posts/41069#top
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3/15/2010 1:38 PM	Rate (0)
little holmes Experienced Member Joined: 12/9/2009 Last visit: 10/30/2025 Posts: 156 Rating: (11)	Hello, via TCP the data are sent as data stream. You can use fixed or variable data length. You have to define and end of message which is interpreted by the receiver. You have toevaluate the end of message in you user program (S7 program). Here you can find more information and some sample programs: http://support.automation.siemens.com/WW/view/en/8707570 http://support.automation.siemens.com/WW/view/en/19033929 Best regards Little Holmes

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Can PLC parse messages using CR+LF?

Created by: vbardelli at: 3/11/2010 9:12 AM (1 Replies)

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vbardelli

Last edited by: O_Moderator at: 3/12/2010 9:37 AM

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