# Cannot connect to device

**URL:** <https://forum.inductiveautomation.com/t/cannot-connect-to-device/104631>\
**Category:** Ignition\
**Tags:** opcua, siemens\
**Created:** [April 3, 2025, 7:43am UTC](https://forum.inductiveautomation.com/t/cannot-connect-to-device/104631 "2025-04-03T07:43:57Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![alessandromarco.ferr](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@alessandromarco.ferr](https://forum.inductiveautomation.com/u/alessandromarco.ferr)\
**Post date:** [April 3, 2025, 7:43am UTC](https://forum.inductiveautomation.com/t/cannot-connect-to-device/104631/1 "2025-04-03T07:43:57Z")

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Hello, I'm using Ignition version 8.1.47, and cannot connect to devices Siemens S7-300 I can reach instead using telnet port 102.  
The gateway logs three types of errors that are looping non-stop, in the specific:

 ![Capture1](https://us1.discourse-cdn.com/inductiveautomation/original/3X/3/2/3214d97524634c3e4a65f16350a1bfca86d3fb3f.jpeg)  
 ![Capture2](https://us1.discourse-cdn.com/inductiveautomation/original/3X/c/3/c3eaf1e83923010cc52bba994ba7419097ce7b8a.jpeg)  
 ![Capture3](https://us1.discourse-cdn.com/inductiveautomation/original/3X/8/7/87156c3c8597c2966c2f46a6ed83109b11843dc3.jpeg)

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<div class="post-metadata">

**Author:** ![David\_Stone](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/david_stone/32/79749_2.png) [@David\_Stone](https://forum.inductiveautomation.com/u/David_Stone)\
**Post date:** [April 3, 2025, 8:51am UTC](https://forum.inductiveautomation.com/t/cannot-connect-to-device/104631/2 "2025-04-03T08:51:16Z")

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S7-300 does not have an OPC-UA server onboard.  
Use the Siemens driver in the devices instead.

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<div class="post-metadata">

**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:** [April 3, 2025, 11:52am UTC](https://forum.inductiveautomation.com/t/cannot-connect-to-device/104631/3 "2025-04-03T11:52:04Z")

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It looks like they already are.

@alessandromarco.ferr this is the kind of error you see when either there is a firewall or network issue (which you've ruled out), or a configuration issue on PLC side - usually something like there's already too many TCP or S7 connections to this PLC and it can't handle any more.

The error you're seeing is basically just the TCP connection being closed immediately by the PLC.