# Modbus TCP Driver Connection Problem **URL:** \ **Category:** Ignition\ **Created:** [June 20, 2019, 4:20am UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970 "2019-06-20T04:20:43Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![leo\_amm](https://avatars.discourse-cdn.com/v4/letter/l/9d8465/32.png) [@leo\_amm](https://forum.inductiveautomation.com/u/leo_amm)\ **Post date:** [June 20, 2019, 4:20am UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970/1 "2019-06-20T04:20:43Z")
I am having problem with Modbus TCP driver. I have configured 2 x IDEC PLC (Acid\_Scrubber and Cyanide\_Scrubber) connected to Ignition Server. Both PLC are having TWO different addresses. 192.168.0.6 and 192.168.0.7 From the Gateway OPC Devices, it can be seen that PLCs are connected to Ignition Server. However, I cannot access the Modbus address/value from the designer by using direct Modbus address. - For example: Not able to read/write **[Acid\_Scrubber]HR10** or **[Cyanide\_Scrubber]HR16** I can only access the Modbus address/values when I use the Modbus unit ID. - For example: Able to read/write **[Acid\_Scrubber]** **1** **.HR10** and/or **[Cyanide\_Scrubber]** **2** **.HR16** I understand that if Modbus TCP devices are using different IP Address then unit ID shouldn’t matter in the addressing format. To me, it doesn’t really matter that I have to use the unit ID addressing. However, the problem is unit ID always changes after a period of time. For example: [Acid\_Scrubber] **1**.HR10 is working fine at one moment and after sometimes, the address is unable to read/write unless I change the Modbus address to [Acid\_Scrubber] **2**.HR10 Further Observation; • From Modbus TCP address mapping, I can poll data for both PLCs using unit ID 1. • However, Tags are usually bad, unspecific. • When I click on the subscribe from gateway quick client, some tags go to Good,specific. • For some other tags, even after clicking on subscribe, it is still bad, unspecific. • If I click on “Read” on gateway quick client, the value returned is Good, specific. • But, after about 3 second, tag goes back to bad, unspecific. Log file can be downloaded here \>\>\> [https://we.tl/t-VOAevEkpjN](https://we.tl/t-VOAevEkpjN) Anyone has faced this problem before and any solution? ---
**Author:** ![denis.palomanes](https://avatars.discourse-cdn.com/v4/letter/d/779978/32.png) [@denis.palomanes](https://forum.inductiveautomation.com/u/denis.palomanes)\ **Post date:** [June 20, 2019, 7:32am UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970/2 "2019-06-20T07:32:40Z")
Hello, We are testing Ignition 8.0.2 and we are facing some similiar problems with the Modbus TCP driver. For some strange reason now we have to indicate the unit ID in some (not all) modbus connection. ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [June 20, 2019, 12:55pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970/3 "2019-06-20T12:55:02Z")
Can you get a Wireshark capture of this behavior as well? ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [June 20, 2019, 3:03pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970/4 "2019-06-20T15:03:23Z")
Your logs are full of messages like this: ```auto 2019-06-16 09:51:03 - drivers.ModbusDriver2.ReadCoilsRequest Received response with ExceptionCode: 0x03 (IllegalDataValue). ``` If the PLC suddenly starts responding with an error code to the exact same requests from Ignition I’m afraid there’s not much else to troubleshoot on the Ignition side - you may need to contact the vendor. Are you using leased scan classes? Have you tried disabling the “Span Gaps” setting? ---
**Author:** ![denis.palomanes](https://avatars.discourse-cdn.com/v4/letter/d/779978/32.png) [@denis.palomanes](https://forum.inductiveautomation.com/u/denis.palomanes)\ **Post date:** [June 21, 2019, 6:42am UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970/5 "2019-06-21T06:42:26Z")
Hi, We have used the wireshark: ![modbus](https://us1.discourse-cdn.com/inductiveautomation/original/2X/7/7d5f36b5f2d593fdd218b33ebe8e9654a803fb04.jpeg) ---
**Author:** ![leo\_amm](https://avatars.discourse-cdn.com/v4/letter/l/9d8465/32.png) [@leo\_amm](https://forum.inductiveautomation.com/u/leo_amm)\ **Post date:** [June 22, 2019, 3:37am UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970/6 "2019-06-22T03:37:26Z")
Hi Kevin, Yes, I have used ModScan, it seems ok and I can see the values. I tried disabling the span Gaps but it doesn’t help. ---
**Author:** ![jorisherry](https://avatars.discourse-cdn.com/v4/letter/j/e19b73/32.png) [@jorisherry](https://forum.inductiveautomation.com/u/jorisherry)\ **Post date:** [June 24, 2019, 7:01am UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970/7 "2019-06-24T07:01:40Z")
Hello I’m also on ignition 8.0.2 and i am also facing modbus problems. I’m getting following error: com.inductiveautomation.ignition.client.gateway\_interface.GatewayException: com.inductiveautomation.ignition.client.gateway\_interface.GatewayException: Driver ‘ModbusTcp’ doesn’t exist. I’m also unable to create tags with ModbusTcp. But i can use ModbusRTUoverTCP. ---
**Author:** ![jorisherry](https://avatars.discourse-cdn.com/v4/letter/j/e19b73/32.png) [@jorisherry](https://forum.inductiveautomation.com/u/jorisherry)\ **Post date:** [June 24, 2019, 8:20am UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970/8 "2019-06-24T08:20:35Z")
Is it illegal to use a colon in the devicename? When I do this, any driver type will stop working. I tried several ways to name my devices. Once i put the colon in, my devices disappear after gateway restart and i can’t see the driver anymore when i try to create new devices… ---
**Author:** ![jay.meinke](https://avatars.discourse-cdn.com/v4/letter/j/ce7236/32.png) [@jay.meinke](https://forum.inductiveautomation.com/u/jay.meinke)\ **Post date:** [July 2, 2020, 6:32pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-driver-connection-problem/25970/9 "2020-07-02T18:32:59Z")
> [@leo\_amm](#): > > y quick client, some tags go to Good,specific. > • For some other tags, even after clicking on subscribe, it is still bad, unspecific. > • If I click on “Read” on gateway quick client, the value returned is Good, specific. > • But, after about 3 second, tag goes back to bad, unspecific. > > Log file can be downloaded here \>\>\> [https://we.tl/t-VOAevEkpjN](https://we.tl/t-VOAevEkpjN) * * * ## ns=1;s=[p1amoh01]1.IR9 worked for me I have an Industrial Arduino running ArduinoModbus.h on port 502. I did not have to create any addressing, I just hard coded the devicename, number (1) and the IR address for the tag. The trick was the "1".