# X_PORT_INVALID

## Means

`PORT` is not a TCP port number

## Typical cause

a platform-injected `PORT` that is empty, non-numeric or out of range — never defaulted past, because a web role that quietly bound 3000 fails the platform's health probe with nothing in the log that names the cause

## Fix

`docker run -e PORT=3000 <image>`

[Config and environment](/error-codes#config-and-environment)