Ports

Service	Port	Notes
Edge proxy (HTTP)	80	Caddy. Redirects to HTTPS
Edge proxy (HTTPS)	443	Caddy. TLS terminates here
Edge admin	unix socket	0600 in rexenv’s config dir — never a TCP port
Embedded DNS	15353 (UDP)	macOS, Linux. On Windows it is 53 — see below
Shared nginx	18088	One server block per site, behind the edge
php-fpm pools	9774, 9780–9785	One pool per installed PHP minor. php-cgi on Windows
php-fpm debug pools	9981–9985	Started on demand for Xdebug-toggled sites (8.1–8.5)
Xdebug DBGp	9003	Your IDE listens. rexenv binds nothing here
FrankenPHP overrides	8200–8299	Per site, loopback only
Apache overrides	8300–8399	Per site, loopback only
OpenLiteSpeed	8400–8499	Per site, loopback only. macOS and Linux
MySQL	13306
MariaDB	13307
PostgreSQL	15432
Redis	16379
Mailpit SMTP	11025
Mailpit web UI	18025
Adminer	no port	Served as an internal vhost through the shared nginx
cloudflared	no port	Outbound-only; nothing listens

Windows differs in two rows, and only two

The DNS answerer binds 53 on 127.0.0.1, not 15353. Windows’ NRPT rule has no port field — it can name a namespace and a name server, and nothing else — so the answerer has to be on the port the resolver will ask. It is loopback-only, which is also why there is no Windows Defender Firewall alert on first run.

The PHP pools are php-cgi, not php-fpm, because php-fpm is not part of the official PHP Windows builds. The port numbers and the formula are unchanged.

Everything else in the table above is the same on Windows as on macOS — except the rows for components the Windows build does not have at all: MariaDB, Redis, Apache, FrankenPHP and OpenLiteSpeed never bind anything there, because they are refused rather than installed.

Linux uses the macOS numbers

Every row above holds on Linux as written — the resolver on 15353, php-fpm pools, FrankenPHP’s and OpenLiteSpeed’s ranges — except the components the Linux build does not have: MariaDB, Redis and Apache never bind anything there, and the debug pools never start, because there is no Xdebug to load. The resolver is a systemd user unit, and a network link, rexenv0, is what sends .rex to it.

Why the odd numbers

They are offset from the usual defaults on purpose. Mailpit’s stock ports are 1025 and 8025, MySQL’s is 3306 — using them would mean rexenv collides with a standalone Mailpit, a MailHog, another local environment, or a database you installed yourself.

The offsets are the difference between rexenv coexisting with your current setup and demanding you dismantle it first.

80 and 443 are the exception

Those cannot be offset. https://yoursite.rex with no port number means 443 — that is the whole point of the URL. If something else already holds them, rexenv names what is holding them instead of failing quietly, and rex doctor reports the same from a terminal.

Binding them costs an admin password on macOS and a password dialog on Linux, where only root may bind below 1024 — on Linux the edge is a root systemd unit — and nothing at all on Windows, where an ordinary account can.

The php-fpm pool numbering is not a range

Pool ports are computed as 9700 + major×10 + minor. That puts PHP 7.4 at 9774, below the 8.x block at 9780–9785, rather than at the start of a tidy contiguous range.

It is the formula being honest rather than the numbers being pretty: the port tells you which version is on the other end of it, and that stays true when a version is added or removed.

Xdebug listens on your side

9003 is the standard DBGp port and it is the only port in this table rexenv does not bind. PHP connects outward to your IDE, so your editor is the listener. That is why the Xdebug toggle needs no port configuration in rexenv — only in your IDE.

Every start is port-gated

Nothing starts without checking its port first. When one is taken, the message names the process holding it and gives a copy-pasteable way to deal with it, rather than reporting a generic failure to start.