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TCP connection between PLC s7-1200 and PC

Created by: eplc at: 6/30/2014 12:57 PM (11 Replies)

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6/30/2014 12:57 PM	Rate (0)
eplc Advanced Member Joined: 3/17/2014 Last visit: 8/31/2021 Posts: 31 Rating: (3)	Hi, I am trying to connect the s7-1200 to the PC with the built-in functions TCON, TSEND and TDISCON. I success when the connection is established by the PC, so I start the TCON function and then connect to the PLC from the PC, but not the other way round. I need the PLC to play as client and connect it to a server, being the PLC who starts the communication. Has someone succeeded on this? TCON is configured in the same way for both approaches, but I ticked where it says who is establishing the connection. As partner for the PLC I am using Hercules software (http://www.hw-group.com/products/hercules/index_en.html) if that helps. Ask me if you need more information, thanks,

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6/30/2014 1:03 PM	Rate (0)
Pittiplatsch Posts: 1368 Rating: (128)	Hello, in the TCON_Param UDT, there is a Parameter "active_est ". FALSE: passive connection establish TRUE: active connection establish
Pittiplatsch Posts: 1368 Rating: (128)
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6/30/2014 1:15 PM	Rate (0)
eplc Advanced Member Joined: 3/17/2014 Last visit: 8/31/2021 Posts: 31 Rating: (3)	Hi, yes, this param is set to TRUE,so the connection establishment is active and will be done by the PLC. But still not working. I am using TCP instead of UDP if that makes any difference. Thanks for your reply

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6/30/2014 1:42 PM	Rate (0)
Pittiplatsch Posts: 1368 Rating: (128)	Hello, are there any errors or/and status codes? Please note, that the error bit and status code are only valid one cycle. So you have to copy these values in another memory area/ variable. like: if errorbit then status_code_save:=status_code: end_if;
Pittiplatsch Posts: 1368 Rating: (128)
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6/30/2014 2:42 PM

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eplc

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Hi,

it gives me the following error:

80A7: Communication error: You called the instruction with COM_RST = 1 before the send job was complete.

but I am not obviously restarting the connection at that point so can I assume that it is not finding the partner to connect? Thanks

6/30/2014 3:17 PM	Rate (0)
Pittiplatsch Posts: 1368 Rating: (128)	Which blocks do you use on PC/PLC side? Comesthe error code "80A7" from "TCON"? This means here"communication error- TDISCON is called before TCON ends".
Pittiplatsch Posts: 1368 Rating: (128)
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6/30/2014 3:54 PM	Rate (0)
eplc Advanced Member Joined: 3/17/2014 Last visit: 8/31/2021 Posts: 31 Rating: (3)	No, sorry I started using TSEND_C as it looks easier all-in-one function. Hope the screenshots make the problem clearer. ss1 is showing the current configuration for TSEND_C. ss2 is showing the TSEND_C ladder code. ss3 is showing how the variables look when I try to connect to the PC by rising edge in CONT input. I am trying to connect to a PC with a simple TCP server on the same port as it is configured in TSEND_C to connect to. Thanks for your help Attachment Screenshots.zip (447 Downloads)

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7/1/2014 10:47 AM	Rate (0)
Pittiplatsch Posts: 1368 Rating: (128)	the Bool-Parameter CONT must be true all the time to hold the connection. do you use the cycle memory of the CPU? This is default MB0, so if you also use M0.0 and so one, the values will be overwritten. The communication connection is terminated when the CONT parameter is set to "0" even if an ongoing data transmission is not complete yet. This does not apply if you are using an already configured connection for TSEND_C. When setting the COM_RST parameter to "1", the currently established connection or a current data transmission can be reset at any time. This terminates the existing communication connection and a new connection is established. If data is being transferred when it executes again, this can lead to a loss of data. To enablethe blockagain after the execution (DONE = 1), call the instruction once with REQ = 0. I can not find an error in your configuration (screenshots) do you know this FAQ: http://support.automation.siemens.com/WW/view/en/67196808?
Pittiplatsch Posts: 1368 Rating: (128)	Last edited by: Pittiplatsch at: 7/1/2014 10:51 AM
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7/1/2014 11:47 AM	Rate (0)
eplc Advanced Member Joined: 3/17/2014 Last visit: 8/31/2021 Posts: 31 Rating: (3)	Hi, I agree with everything you said, that is how I am doing it and this is why it looks so weird. However there are a couple of details that may give us some hints: With the same configuration as it is shown, just by checking de radio button from active to passive, it works fine, which makes me wonder if there will be another needed change for it to work as active from passive. TCP sequence is SYN, SYN+ACK and ACK between server and client for the handshake. When the PLC is acting as passive, the sequence is completed and fine, but when it is acting as active, it sends the SYN message, but doesnt get any reply (SYN+ACK). There is a subtle difference between the two SYN's messages in the two tests: SYN from PLC doesnt have WS (Window Scaling) nor SACK_PERM (Selective Acknowlegments Permitted). Can this be causing any issue? Thanks for your help!

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7/1/2014 12:46 PM	Rate (1)
Pittiplatsch Posts: 1368 Rating: (128)	Hello, could the firewall cause this problem? Can you switch of the firewall on PC and tray again with PLC = active? Just one more idea...
Pittiplatsch Posts: 1368 Rating: (128)
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TCP connection between PLC s7-1200 and PC

Created by: eplc at: 6/30/2014 12:57 PM (11 Replies)

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Created by: eplc at: 6/30/2014 12:57 PM (11 Replies)

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