Post by fabian on v3.5 SP19 - Modbus TCP Devices - Channel Limit? ^{CODESYS Forge talk (Post)}
Hi all, Is there an update on this topic? Same problem here, I can not add more than 10 Modbus-Slave channels. Is there a workaround? Many thanks! Fabian Codesys 3.5.19 SP2, Modbus 4.3.0.0, Name: Modbus TCP Slave Hersteller: 3S - Smart Software Solutions GmbH Kategorien: Modbus TCP Slave Typ: 89 ID: 0000 0005 Version: 4.1.0.0 Bestellnummer: - Beschreibung: Ein Geraet, das als Slave für einen Modbus TCP Master konfiguriert ist. Version Konfiguration 3.5.11.0
Last updated: 2023-08-28

Post by george32 on TCP Server ^{CODESYS Forge talk (Post)}
Dear people, I would like to create a TCP server in my PLC program. The TCP server needs to communicate with an external device. I have been searching the internet and found that the libraries Syssocket or CAA NetBaseSrv are two possible solutions to create a TCP server. From what I have read, CAA NetBaseSrv is more user-friendly to implement than the Syssocket variant. However, I am still struggling to actually implement this library. Foremost is my little knowledge about creating a TCP server and how to read/understand each function block, especially the outputs of some blocks and the types, e.g. server has an output CAA.Handle, but I cannot find the explanation of CAA.Handle. I tried to find a good document that can help me understand how to implement a TCP server, but I could not find it. Thank you in advance, George
Last updated: 2025-02-20

Post by rmaas on TCP Server ^{CODESYS Forge talk (Post)}
Hi George, I am no expert but recently tried and got it working using this example project: https://forge.codesys.com/prj/codesys-example/nbs/home/Home/#example-for-tcp-server-tcp-client BR, Rinie
Last updated: 2025-02-20

Post by ph0010421 on MODBUS TCP REGISTERS CODESYS V3.5 ^{CODESYS Forge talk (Post)}
hello Use FC3 instead of FC4
Last updated: 2024-10-11

Post by bartspako on Connection between Beijer PLC and Schneider Tesys-Island using Modbus TCP ^{CODESYS Forge talk (Post)}
Last updated: 2024-10-16

Post by eschwellinger on v3.5 SP19 - Modbus TCP Devices - Channel Limit? ^{CODESYS Forge talk (Post)}
Guess you could just add two modbus slaves with the same ip, to enlarge the 10 channel limit.
Last updated: 2023-08-28

Post by squiggleypuff on Can't Add New Version of Modbus TCP Master ^{CODESYS Forge talk (Post)}
Bumping for visibility, still unable to get Modbus working on this thing.
Last updated: 2024-04-08

Post by eschwellinger on Modbus TLS Kommunikation ^{CODESYS Forge talk (Post)}
aktuell bin ich mir nicht sicher ob das Modbus/TCP Security Protocol unterstützt, ich check das mal. Hast du ein Handbuch zu der Wallbox?
Last updated: 2025-11-06

Post by danp1406 on Question about Demo License limitations for Modbus TCP communication and Fieldbus Instances ^{CODESYS Forge talk (Post)}
Hello everyone, I am currently working with CODESYS Virtual Control for Linux running in Docker on a Debian virtual machine. I am deploying my application using Deploy Control SL, and in my project I am using the ModbusFB library to implement Modbus TCP communication. My setup is the following: I am trying to establish a Modbus TCP connection between a virtual PLC (CODESYS acting as Modbus TCP Client/Master) and a Siemens S7-1200 PLC acting as a Modbus TCP Server. From the Debian VM, I can successfully ping the S7-1200 and verify that port 502 is open using tools like nc. Network-wise, everything appears to be correct. However, when running the application in CODESYS, I receive messages such as “Demo mode for Modbus/TCP Master started. Will expire and stop!” and socket errors like “ClientSocket.UpdateStatus socket error 111 disconnecting.” The ClientTCP block from the ModbusFB library attempts to connect, but the connection does not remain stable. My main question is whether the CODESYS demo license explicitly limits or interrupts Modbus TCP Master communication. Is it expected that in demo mode the runtime will automatically close sockets after some time or prevent stable Modbus TCP connections? I would like to confirm whether this behavior is normal when using ModbusFB in demo mode, or if I should continue troubleshooting the configuration. Additionally, I would like clarification regarding the “fieldbus instances” mentioned in CODESYS licensing options (for example, 2, 4, or 16 instances). What exactly is considered one fieldbus instance? Does one Modbus TCP Client block count as one instance? Does each active connection to a different device count separately? Do Modbus TCP Master and Server count independently toward the total number of instances? Finally, I would appreciate clarification on any other practical limitations of demo mode when using industrial communication libraries such as ModbusFB. Are there limits on the number of connections, number of requests, or communication duration? I am trying to determine whether demo mode is sufficient for testing a virtual PLC communicating with a Siemens S7-1200 over Modbus TCP, or whether a full license is required even for this kind of validation scenario. Thank you in advance for any guidance.
Last updated: 2026-02-25

Post by banialuk on Modbus TCP Server ^{CODESYS Forge talk (Post)}
Hello, I have poroblem with define input in function block modbusFB.serverTCP 'dataModel', in my aplication I need starting Input Registers from 3000, and I must define this in 'data Model' but I dont now how exacly to do it. Anybody now somethin about this?
Last updated: 2024-10-19

Post by timvh on Modbus TCP Server connection is ESTABLISHED but all holding registers are value 0? ^{CODESYS Forge talk (Post)}
Are you sure you need to read holding registers? Have you tried reading input registers?
Last updated: 2026-01-07

Post by fleaplc on Modbus TCP Server connection is ESTABLISHED but all holding registers are value 0? ^{CODESYS Forge talk (Post)}
Did you check the communication with a sniffer ? (ex. Wireshark) to check if the holding get to zero by a wrong writing (client initialization?) o something else?
Last updated: 2026-01-27

Post by winki on Modbus TCP & RTU with Control for Linux SL ^{CODESYS Forge talk (Post)}
Hello, Today I am able to test ma industrial computer in my test bench. I am able to do all the configuration throught my VPN, 100% remote. I can see the gateway & the Virtual PLC. Now I would like to do some Modbus TCP Client & Modbus RS485. But I am lost due to docker ! When I go to modbus TCP it only gave me the docker network, but not my eth0 & eth01 When I go to modbus rtu, how can I create the link between Com number & my /dev/ttyRS485 Loic,
Last updated: 2024-10-23

Post by fmon on Modbus TCP client reconnection problem ^{CODESYS Forge talk (Post)}
Hello, I am using codesys Modbus TCP client (4.4.0.0) to communicate with a python modbus server (package pyModbusTCP). I first start my python server on the distant machine. After a fresh codesys compilation, a plc connection/transfer and a PLC run, the modbus connection is OK. Every time in this context the connection is created correctly. When I shut down the server, the modbus connection falls, that is normal. When I restart the python server, impossible to recreate the modbus connexion. With the client autoreconnection, I see on my server that the client tries to connect but unsuccesfully. I have the following message : DEBUG:pyModbusTCP.server:accept new connection from ClientInfo(address='192.168.1.20', port=33476) DEBUG:pyModbusTCP.server:Exception during request handling: NetworkError('recv return null') I tried to stop the codesys client and to restart it with these commands : Modbus_TCP_Client.xStop := True; // Or False Modbus_TCP_Client.Enable := True; // Or False Modbus_TCP_Server.Enable := True; // Or False I tried to confirm the error manually to force reconnection with: Modbus_TCP_Server_Motors.xConfirmError := TRUE; I tried also this command to STOP/RESET/START client and server (codesys side) but nothing happens : status_client := Modbus_TCP_Client.SetCommunicationState(eRequestedState := DED.DEVICE_TRANSITION_STATE.STOP); // .RESET & .START The answer of this function when executed is "status_client = NOT_SUPPORTED". Is it normal ? It seems that is a socket problem, but I do not understand if it is on the client or server side. I tried a modbus simulator called "ananas.exe" and the result is the same. Impossible to get a modbus client reconnection. What is different at the first client connection and at a reconnection attempt ? Thanks for your help
Last updated: 2025-03-17

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