# Modbus Connection or Addressing Issue **URL:** \ **Category:** Ignition\ **Tags:** ignition81\ **Created:** [April 3, 2025, 9:47pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681 "2025-04-03T21:47:06Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![elijah.roberts](https://avatars.discourse-cdn.com/v4/letter/e/a6a055/32.png) [@elijah.roberts](https://forum.inductiveautomation.com/u/elijah.roberts)\ **Post date:** [April 3, 2025, 9:47pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/1 "2025-04-03T21:47:06Z")
I have discovered I know very little about Modbus addressing today. So I have a UPS that has a network card for Modbus TCP. The slave Id is set to 1 and the port is 502. Ignition can connect to the device and I can ping it on the network, but when i try to create tags I get this error: ```python java.lang.Exception: Request failed by TimeoutDaemon due to timeout: ScheduledRequest[com.inductiveautomation.xopc.drivers.modbus2.requests.ReadHoldingRegistersRequest@72f8e1af] at com.inductiveautomation.xopc.driver.api.BasicRequestCycle$TimeoutDaemon.failRequests(BasicRequestCycle.java:376) at com.inductiveautomation.xopc.driver.api.BasicRequestCycle$TimeoutDaemon.run(BasicRequestCycle.java:328) at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) at java.base/java.util.concurrent.FutureTask.runAndReset(Unknown Source) at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.base/java.lang.Thread.run(Unknown Source) ``` Is this error stating the comms to the device is bad, or that my tag addressing is bad. For what its worth it could very well be the tag. The manual looks like this ![Screenshot 2025-04-03 164414](https://us1.discourse-cdn.com/inductiveautomation/original/3X/a/3/a36a59633b1c3e7e5c117e2d1eeebac2a8c0ff31.png) My tag addressing I assumed it was is: ```python [DeviceName]HR768 ``` I also have zero based addressing for my device turned on, since that is what it sounded like the manual was saying the network card is setup for. Any advice would be appreciated thanks! ---
**Author:** ![ryan.white](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ryan.white/32/73193_2.png) [@ryan.white](https://forum.inductiveautomation.com/u/ryan.white)\ **Post date:** [April 3, 2025, 9:50pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/2 "2025-04-03T21:50:45Z")
> [@elijah.roberts](#): > > I can ping it on the network Can you ping this device directly from the server hosting your ignition gateway? That's what matters. Check firewall rules on the gateway machine and make sure you allow TCP traffic on port 502 ---
**Author:** ![Cody\_Morgan](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cody\_Morgan](https://forum.inductiveautomation.com/u/Cody_Morgan)\ **Post date:** [April 3, 2025, 9:52pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/3 "2025-04-03T21:52:33Z")
Why are you using `C768`? The screenshot from the manual you shared shows Holding Registers, which is an `HR` notation in the Modbus driver. Try `[DeviceName]HR768` to start. You may need `[DeviceName]1.HR768` since you note that the slave ID is 1. Ignition defaults to 0, which many Modbus devices do not appreciate. Edit: Also make sure zero based addressing is checked in the advanced settings for the device connection. The manual you shared says addresses are 0 based. ---
**Author:** ![elijah.roberts](https://avatars.discourse-cdn.com/v4/letter/e/a6a055/32.png) [@elijah.roberts](https://forum.inductiveautomation.com/u/elijah.roberts)\ **Post date:** [April 3, 2025, 9:52pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/4 "2025-04-03T21:52:51Z")
Yes I can ping it from the server. And I do have 502 opened as well. That was one of the first things I tried thinking it was the issue. ---
**Author:** ![elijah.roberts](https://avatars.discourse-cdn.com/v4/letter/e/a6a055/32.png) [@elijah.roberts](https://forum.inductiveautomation.com/u/elijah.roberts)\ **Post date:** [April 3, 2025, 9:54pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/5 "2025-04-03T21:54:53Z")
Sorry yes, I meant to say HR not C. I'll be sure to edit that. Although even when I try those address examples the tag still returns as _Bad_ ---
**Author:** ![Cody\_Morgan](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cody\_Morgan](https://forum.inductiveautomation.com/u/Cody_Morgan)\ **Post date:** [April 3, 2025, 10:00pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/6 "2025-04-03T22:00:02Z")
Can you get a Wireshark capture while using `[DeviceName]1.HR768`? ---
**Author:** ![elijah.roberts](https://avatars.discourse-cdn.com/v4/letter/e/a6a055/32.png) [@elijah.roberts](https://forum.inductiveautomation.com/u/elijah.roberts)\ **Post date:** [April 3, 2025, 10:08pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/7 "2025-04-03T22:08:38Z")
I will get that tomorrow morning, I am off site currently and the UPS isn't accessible remotely. I'll post the results here. Thank you for your help! ---
**Author:** ![elijah.roberts](https://avatars.discourse-cdn.com/v4/letter/e/a6a055/32.png) [@elijah.roberts](https://forum.inductiveautomation.com/u/elijah.roberts)\ **Post date:** [April 4, 2025, 2:13pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/8 "2025-04-04T14:13:48Z")
[capture.pcap](https://forum.inductiveautomation.com/uploads/short-url/slKsougviiO7BiaSDoqGuIHred0.pcap) (6.7 KB) Heres is the Capture file. I let it run for roughly a minute with that tag address in there as you suggested. If I need to run it longer I can do that as well. ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [April 4, 2025, 2:20pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/10 "2025-04-04T14:20:32Z")
Your device is accepting the TCP connection, but not ever replying to Modbus TCP queries. There is likely some misconfiguration on the device side. You may need help from that device manufacturer. ---
**Author:** ![elijah.roberts](https://avatars.discourse-cdn.com/v4/letter/e/a6a055/32.png) [@elijah.roberts](https://forum.inductiveautomation.com/u/elijah.roberts)\ **Post date:** [April 4, 2025, 2:23pm UTC](https://forum.inductiveautomation.com/t/modbus-connection-or-addressing-issue/104681/11 "2025-04-04T14:23:29Z")
Thank you Phil.