Post by pra83 on CODESYS SoftRedundancy — Both PLCs stay standalone after network interruption — Auto recovery not working ^{CODESYS Forge talk (Post)}
Hello, We are facing a critical issue with CODESYS SoftRedundancy that we have been unable to resolve despite extensive troubleshooting. HARDWARE: 2× HP EliteDesk 800 G9 SFF Intel Core i7-14700 (20 cores) 16GB RAM, 512GB NVMe SSD Windows 11 IoT Enterprise LTSC 2024 NIC1: Built-in Intel GbE NIC2: Intel I210-T1 PCIe (NIC team) SOFTWARE: CODESYS Control Win V3 - x64 Version 3.5.22.10 CODESYS SoftRedundancy SL Server 1 IP: 172.10.10.101 (PLC1 — Active) Server 2 IP: 172.10.10.102 (PLC2 — Standby) CURRENT CODESYSControl.cfg: [CmpRedundancy] BootupWaitTime=120000 StandbyWaitTime=12100 SynchronousTimeout=12100 [CmpSchedule] ProcessorLoad.Maximum=80 WatchdogTime=12000 WatchdogTimeoutAction=0 CONFIRMED WORKING: PLC1/PLC2 identification configured via IDE Connection IP configured via IDE AutoSync enabled and written via IDE Normal Active/Standby operation working Server 2 auto-promotes when Server 1 completely fails PROBLEM DESCRIPTION: When NIC1 cable is removed from Server 1 — both servers go to standalone mode. When NIC1 cable is reconnected — both servers remain in standalone indefinitely. Neither server auto-recovers to Active/Standby without manual CODESYS service restart. AutoSync fires (!!! Autosync !!! visible in log) but recovery does not complete. Tested with direct cable (no NIC team) — same result. Confirmed not a hardware or NIC teaming issue. KEY LOG MESSAGES: "Timeout: No sync message RMSG_StartCycle (5) from master: Standalone" "Socket on other side closed gracefully 0" "Standby PLC: Open acyclic work socket failed" "Connection broke after 11806ms. Check BootupWaitTime." Autosync(fires but does not complete recovery) PCAP ANALYSIS (Wireshark): CODESYS sync stops completely at T+3s Server 1 sends TCP FIN on ports 1206 and 1208 at T+5s No CODESYS redundancy traffic for remaining 24 seconds Both servers stay standalone indefinitely WHAT WE HAVE TRIED: StandbyWaitTime = 12100ms SynchronousTimeout = 12100ms WatchdogTime = 12000ms (less than StandbyWaitTime) AutoSync enabled NIC2 set as Standby adapter Disabled Windows Network Discovery Direct cable test — rules out NIC hardware QUESTION: Per official CODESYS documentation: "No automatic Reconnect is included in the functional scope of the redundancy components. You can program the triggering of a reconnect." Is RDCY.Synchronize() the correct function to add to our application for automatic recovery after both PLCs go standalone? What is preventing auto-recovery when AutoSync is enabled and PlcIdent is correctly set? Thank you for your support.
Last updated: 2026-05-02

Post by winki on ModbusFB ClientRequest: never recovers after a single ReplyTimeout (requires full download) ^{CODESYS Forge talk (Post)}
Library: ModbusFB (CODESYS Modbus package) IDE / Runtime: CODESYS V3.5 SP___ / Control runtime ___ Target: ___ (e.g. gateway, Linux ARM64 / Debian) Slave: Modbus TCP inverter Summary I poll a Modbus TCP slave with a permanent connection: one ClientTCP (kept connected, xConnect:=TRUE) and one ClientRequestReadHoldingRegisters, triggered cyclically. Everything works fine after a fresh application download. But as soon as one single ReplyTimeout occurs (slave temporarily not answering), the request never recovers. It stays stuck and no further messages are sent, even though the TCP connection is still reported as alive. Only a full application download brings it back — an online change or a runtime reset is not enough / not what I want in production. State observed when stuck So the connection is alive, the request finished in ReplyTimeout, the FB is back to _state = None, but udiNumMsgSent no longer increases — as if a new rising edge on xExecute is no longer accepted / no longer produces a new message. My trigger logic (simplified) Each PLC cycle, in this order: If the request is fully at rest (NOT xExecute AND NOT xBusy AND NOT xDone AND NOT xError) and a read is pending, I set xExecute := TRUE. I call clientTcp() then clientRequest(rClient := clientTcp) once each, per cycle. On xDone or xError, I set xExecute := FALSE. I made sure to insert at least one full cycle with xExecute = FALSE (seen by the FB call) before re-triggering, so the falling edge is processed. Questions After a ReplyTimeout (xError = TRUE), what is the exact, correct sequence to re-trigger the same ClientRequest so a new message is actually sent again? Is a full cycle with xExecute = FALSE between two executions mandatory? Is there a known condition where, after ReplyTimeout, the ClientTCP keeps xConnected = TRUE but silently stops sending new requests (e.g. an internal request queue / _udiRequestId that gets out of sync)? udiNumMsgSent freezing at 23 while the FB shows _state = None is what puzzles me. Is the recommended pattern to drop the connection (ClientTCP.xConnect := FALSE for one cycle, then TRUE) on a request error, rather than keeping it alive? The docs state a request error does not close the connection, so I kept it open — but maybe that is the issue here. Could the large uiStartItem (50514) be relevant? It works right after download, so addressing seems correct, but I want to rule it out. Any guidance on the canonical recovery pattern after a request timeout would be greatly appreciated. Thanks!
Last updated: 7 days ago

Post by simover on TCP/IP client ^{CODESYS Forge talk (Post)}
HELLO thank for you answer!! I'm a beginner can you give me an example?
Last updated: 2023-12-19

Post by kuegerls on OpC UA server on Raspberry Pi MC SL - Certificate Issue ^{CODESYS Forge talk (Post)}
Hello, I have set up an OPC UA server following several guides, including this one: https://revolutionpi.com/documentation/tutorials/opc-ua-codesys-nodered/. The license for the runtime is installed on the device. However, I am unable to create a certificate for the OPC UA server in the security screen. I always get the error message: "The certificate has not been created by the device." Does anyone have an idea what might be causing this issue? Any help would be greatly appreciated! Thanks in advance! Best regards, Stefan
Last updated: 2025-04-02

Post by timl on BacNet Server ^{CODESYS Forge talk (Post)}
Hallo, für einen BacNet2 Server lassen sich mit zwei Ethernet Schnittstellen auch zwei Bacnet 2 IP Datalinks anlegen. Einen Datalink nutze ich für den UDP Port 47808 und einen für den UDP Port 47809. Dadurch ist der Server aus beiden Netzwerken erreichbar, was so gewollt ist. Allerdings verbindet er die beiden Netze auch miteinander, was zu Kommunikationsproblemen führt, da in beiden Netzwerken bereits gleiche Device ID's vergeben sind und diese sich dann doppeln. Lässt sich diese Verbindung der beiden Netze abschalten? Gruß Tim
Last updated: 2024-02-20

Post by miodusy on File transfer via visu and codesys automation server ^{CODESYS Forge talk (Post)}
I have a problem with the file transfer library. Namely, it does not work via the codesys server. (error 5; overtime, and visualization resets). They operate mostly in local chains. I tested different browsers and VPN from the router. It works everywhere, except through access from the codesys automation server. The client, having many machines under one account, prefers to keep it that way rather than use an individual VPN just to download a backup. Does anyone have an idea what the problem is? Sylwester M.
Last updated: 2024-03-07

Post by yannickasselin on codesys VLAN tagging ^{CODESYS Forge talk (Post)}
I ordered a cheap managed switch and tested it as soon as I received the switch. It works great! I even went a bit further. As you can see in the screenshot, I created 2 Codesys containers. Each one having 2 fieldbuses. The first one has EtherCAT and EtherNet/IP and the second one has EtherCAT and Modbus/TCP. All going through the same ethernet port from the PC to the switch. The switch splits it up into 4 different networks. The hardest part was to figure out how to configure the switch. @eschwellinger, thank you very much.
Last updated: 2024-09-17

Post by timvh on Modbus TCP & RTU with Control for Linux SL ^{CODESYS Forge talk (Post)}
It seems you have 2 network interfaces. Did you try eth1? Did you already configure the IP address for this interface in Linux? If yes, then maybe undo this. - or only set eth0 in the Nic configuration without anything else (so no IP address, because this is already set in Linux). For more information about the Nic settings, see (probably already read it?): https://content.helpme-codesys.com/en/CODESYS%20Control/_rtsl_obj_deploy_control_sl_configuration.html PS, if you only want to run CODESYS Control SL, you don't necessarily need the Virtual PLC variant. You could also install and run the CODESYS Control SL Runtime in the Host operating system. This way you should also be able to access the serial port and directly access all ethernet ports. Maybe this is easier?
Last updated: 2024-10-23

Post by jroddball79 on PM556-TP-ETH — How to change IP address without overwriting the PLC program? ^{CODESYS Forge talk (Post)}
Still looking for a solution. I have gathered more information that might help: Device: ABB AC500 PM556-TP-ETH Firmware version: 2.4.2.14993 (dated 2014) Open ports confirmed: 502 (Modbus TCP), 1200 and 1201 (CODESYS runtime). SSH (22) and HTTP (80) are not reachable. No SD card in the PLC. I can connect via Automation Builder using the current IP and Online Login works, but I have no original source project available. Automation Builder requires a full PLC download to apply IP changes, which we want to avoid as it would overwrite the running program. Any guidance on how to change the IP without a full download would be greatly appreciated. I am also open to solutions using third party tools, DCP protocol, or scripts. Thank you
Last updated: 2026-05-22

Post by yannickasselin on Question about Demo License limitations for Modbus TCP communication and Fieldbus Instances ^{CODESYS Forge talk (Post)}
As far as I know, there is no other limitations than the 2 hours limit. The demo mode should be plenty enough for testing purposes. Regarding instances. In the device tree, 1 master = 1 instance, no matter how many slaves the master is communicating with. But it is also possible that your Codesys runtime act as a slave. In this case, each slave in the device tree is one instance. You can also use the license metric tool in the IDE. This will tell you exactly how many instances you have in your project. https://content.helpme-codesys.com/en/CODESYS%20Development%20System/_cds_edt_device_licensed_software_metrics.html
Last updated: 2026-02-28

Post by jroddball79 on PM556-TP-ETH — How to change IP address without overwriting the PLC program? ^{CODESYS Forge talk (Post)}
We have checked open ports. SSH (22) and HTTP (80) are not reachable. The only open ports are: 502 (Modbus TCP — used for lighting control) 1200 (CODESYS runtime) 1201 (CODESYS runtime) We can connect via Automation Builder using the current IP, but we don't have the original project source — only an empty project. This is why we are afraid of doing a full download, as it would overwrite the running application. Is there any way to change the IP through the CODESYS runtime protocol on ports 1200/1201 without affecting the running program?"
Last updated: 2026-05-20

Post by brell on Automatic xExecute NBS.TCP_write ^{CODESYS Forge talk (Post)}
I've recently started experimenting with CODESYS for a project and am fairly new to it. I'm currently working with Function Block Diagrams (FBD) to set up TCP communication between a server and a client, where the client is implemented as a Python script. Once the communication is established, my connection status changes to True, which is the expected behavior. My challenge arises with the TCP write module, which requires the xEnable_write flag to toggle between True and False. If xEnable_write remains True, the module only performs a single write operation. To address this, I introduced a falling edge trigger (F_TRIG), expecting it to help in toggling xEnable_write and it does, However, I've encountered an issue where in the beginning after connxion established I need to manually set xEnable_write to True for the system to work as intended. I'm looking for a way to automate this process so that xEnable_write becomes True automatically upon establishing a connection . Initially, I tried setting xEnable_write to True from the start, but this approach didn't work well since it left the flag permanently True, preventing further toggling. I also experimented with using a TON timer, but I faced similar issues. I am seeking a solution that automatically toggles xEnable_write between True and False after a connection is established, ensuring continuous write operations without manual intervention. Any advice or guidance on how to achieve this would be greatly appreciated."
Last updated: 2024-03-05

Post by shrikantp007 on new to codesys help on modbus with ardunio modbus rtu ^{CODESYS Forge talk (Post)}
Hello , I am new to codesys ,working with it for just 15-17 days so ,i think i am able to installed it and configure it ,not i want to use ardunio program (smart dustbin ,college project using motor and Ultrasonic Module HC-SR04 and servo motor). i use ardunio program to write code with chatgpt to work ardunio as a modbus rtu as i dont have ethernet or wifi shild ,i wrote program in ariduno but now don have idea what change i have to make in codesys to comunicate as modbus slave it give error with bus error ,where i can get all errors ? Thanks in advance :)
Last updated: 2024-07-21

Post by mystx on Timeout Error in Modbus Communication with WAGO PFC200 and iEM2050 Meter using 750-652 Module ^{CODESYS Forge talk (Post)}
Hello I have the same problem, anyone have some idea?? Regards
Last updated: 2024-07-30

Post by mystx on Timeout Error in Modbus Communication with WAGO PFC200 and iEM2050 Meter using 750-652 Module ^{CODESYS Forge talk (Post)}
Hello I have the same problem, anyone have some idea?? Regards
Last updated: 2024-07-30

Post by mystx on Timeout Error in Modbus Communication with WAGO PFC200 and iEM2050 Meter using 750-652 Module ^{CODESYS Forge talk (Post)}
Hello I have the same problem, anyone have some idea?? Regards
Last updated: 2024-07-30

Post by thysonfury on OPTO22 Groov Epic PR2 Modbus Comms Dropping out every 2 hours and 4 Mins ^{CODESYS Forge talk (Post)}
OPTO22 Codesys Activation license not active.
Last updated: 2024-09-11

Post by zdenekkrejci on Issues with Modbus Slave with Raspberry Pi ^{CODESYS Forge talk (Post)}
Did you find out what was wrong? I have the same issue
Last updated: 2025-03-09

Post by zdenekkrejci on Issues with Modbus Slave with Raspberry Pi ^{CODESYS Forge talk (Post)}
Did you find out what was wrong? I have the same issue
Last updated: 2025-03-09

Post by eschwellinger on ModbusTCP RaspberryPi zu Fronius Wechselrichter ^{CODESYS Forge talk (Post)}
Schreibe den Slavename(der vom Gerätebaum) in ein Watchfenster dann siehst du Instanz des Modbus Slave Fb's und hast dadurch Diagnose Info
Last updated: 2025-07-04

Post by solidlogicguy on Little endian to Float from Modbus RTU ^{CODESYS Forge talk (Post)}
Just tried and returns the same value but in scientific notation.
Last updated: 2024-01-08

Post by tomast on Siemens V20 Frequenzumrichter über Modbus RTU ^{CODESYS Forge talk (Post)}
Hi Tim, Have you sorted out your problem because i have also problems with i?
Last updated: 2024-03-21

Post by dawidr on Timeout Error in Modbus Communication with WAGO PFC200 and iEM2050 Meter using 750-652 Module ^{CODESYS Forge talk (Post)}
Last updated: 2024-04-07

Post by csanderson on IoDrvModbusTCP_Diag not defined when using MODBUS ^{CODESYS Forge talk (Post)}
I am also having this same issue after upgrading to 3.5.20.0. Any help Codesys?
Last updated: 2024-04-17

Post by santana on IoDrvModbusTCP_Diag not defined when using MODBUS ^{CODESYS Forge talk (Post)}
I'm having this same issue. I upgraded to 3.5.20.0 from 3.5.19.20. Now I have the precompile errors shown above.
Last updated: 2024-04-17

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