# Stream position data from .json and send servoj() commands

**URL:** <https://forum.universal-robots.com/t/stream-position-data-from-json-and-send-servoj-commands/42097>\
**Category:** URScript\
**Created:** [January 22, 2026, 9:39pm UTC](https://forum.universal-robots.com/t/stream-position-data-from-json-and-send-servoj-commands/42097 "2026-01-22T21:39:39Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![mat.elwarth](https://avatars.discourse-cdn.com/v4/letter/m/3e96dc/32.png) [@mat.elwarth](https://forum.universal-robots.com/u/mat.elwarth)\
**Post date:** [January 22, 2026, 9:39pm UTC](https://forum.universal-robots.com/t/stream-position-data-from-json-and-send-servoj-commands/42097/1 "2026-01-22T21:39:39Z")

</div>

Hi,

I cannot quite find a forum thread for to help my use-case.

I’m developing a URCap, which, among other things, I want to be able to traverse through a large amount of position data I store in a .json file in a folder in the /programs/ folder. From a toolbar, at the click of a button I want to stream the data from the .json and send servoj() commands to the robot to smoothly traverse back through the positions. I have the delta\_t it took to reach each position from the last stored as well for acceleration and deceleration ramping.

For some time I was trying to send servoj commands over the secondary client (port 30002), but from what I’ve read this doesn’t work for real-time control. From looking on the forum, it is recommended to use port 30004 and an RTDE loop, but I don’t want to control the robot remotely. I want to send commands from user interactions with the teach pendant.

For some extra context I use an XML-RPC python daemon to send the positions to the .json, and I’m developing for an e-series.

Any help would be appreciated. Thanks!