# Fixed port for service

**URL:** <https://forum.opencyphal.org/t/fixed-port-for-service/1732>\
**Category:** General\
**Created:** [August 4, 2022, 5:48pm UTC](https://forum.opencyphal.org/t/fixed-port-for-service/1732 "2022-08-04T17:48:51Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![digitecomg](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/digitecomg/32/1215_2.png) [@digitecomg](https://forum.opencyphal.org/u/digitecomg)\
**Post date:** [August 4, 2022, 5:48pm UTC](https://forum.opencyphal.org/t/fixed-port-for-service/1732/1 "2022-08-04T17:48:51Z")

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If one wanted to create a fixed port from the DSDL eg. 100.rmap.module.Test.1.0 (Data type definition v1.0 with fixed port-ID 100), I read from the specification that it is allowed although not recommended. It’s correct?

Specifications to  
Table 2.1 (page 5): Data type taxonomy

(Private → Fixed port identifiers)

Using ranges: → Subject-ID Service-ID Purpose  
[0, 6143] [0, 255] Unregulated identifiers (both fixed and non-fixed).

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**Author:** ![pavel.kirienko](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/pavel.kirienko/32/9_2.png) [@pavel.kirienko](https://forum.opencyphal.org/u/pavel.kirienko)\
**Post date:** [August 5, 2022, 7:27am UTC](https://forum.opencyphal.org/t/fixed-port-for-service/1732/2 "2022-08-05T07:27:45Z")

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Yes, it is possible, but strongly discouraged, consider this an anti-pattern. If you must, you can create one, but be sure that your definitions are not available to the public or any third parties because that would risk creating conflicting port-IDs.