# Inconsistent modbus server access

**URL:** <https://forum.universal-robots.com/t/inconsistent-modbus-server-access/22023>\
**Category:** Robot Communication\
**Created:** [June 16, 2022, 3:05pm UTC](https://forum.universal-robots.com/t/inconsistent-modbus-server-access/22023 "2022-06-16T15:05:22Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![anon96495344](https://avatars.discourse-cdn.com/v4/letter/a/4af34b/32.png) [@anon96495344](https://forum.universal-robots.com/u/anon96495344)\
**Post date:** [June 16, 2022, 3:05pm UTC](https://forum.universal-robots.com/t/inconsistent-modbus-server-access/22023/1 "2022-06-16T15:05:22Z")

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I’m having very inconsistent results access the modbus server of the UR.

Node Red shows a connection, but any attempt to read registers causes the connection to fail and reports “Port not open” but nmap shows it is.

Simply Modbus can’t read registers but modscan64 can.

I’m currently running Polyscope 5.11.11, should I downgrade?

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**Author:** ![anon96495344](https://avatars.discourse-cdn.com/v4/letter/a/4af34b/32.png) [@anon96495344](https://forum.universal-robots.com/u/anon96495344)\
**Post date:** [June 16, 2022, 8:31pm UTC](https://forum.universal-robots.com/t/inconsistent-modbus-server-access/22023/2 "2022-06-16T20:31:43Z")

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Interestingly I can form a modbus TCP packet manually and use a plain TCP node and it works…