# Port forwarding

Local port forwarding lets you reach services behind your server — a database,
a notebook, a dev server — from your device as if they were local.

## Adding a rule

Open a host in the editor and go to the **forwarding** tab. Each rule is:

- **local port** — the port on your device (must be 1024 or higher; the iOS
  sandbox can't bind below that),
- **remote host** — as seen from the SSH server (default `localhost`),
- **remote port**,
- an optional **label**,
- **auto-start when connecting**.

Presets cover the usual suspects: jupyter 8888, postgres 5432, mysql 3306,
redis 6379, web 3000, web 8080.

Local ports can't repeat within one host. Edits to rules apply live to an
already-connected host.

![The forwarding tab of the host editor with one rule: local port 8080 to localhost:18080, labelled dev server, with an enable toggle.](https://bambouville.com/docs/assets/img/forwarding-rule.png)

*A saved rule in the host editor's forwarding tab, with its enable toggle and current state.*


## The tunnels page

The sidebar's **tunnels** page gathers every forwarding rule across all your
hosts, grouped by host with connected/disconnected status. Each rule shows its
state (e.g. "listening · 0 active"), live ↑/↓ byte counters, an enable toggle,
and a button to open HTTP-ish ports in Safari.

Inside a session, a **⇄ N** chip in the top bar shows the same state for that
host.

On [iPhone](https://bambouville.com/docs/iphone/), tunnels are visible from the session top bar but
rules are created and edited on iPad.

![The tunnels page listing one forwarding rule, 8080 to localhost:18080 labelled dev server, grouped under a connected host and showing its listening state with an enable toggle.](https://bambouville.com/docs/assets/img/tunnels-page.png)

*Every rule across every host, grouped by host, with live state and a toggle each.*


## Using a tunnel

Once a rule is listening, point any app on the device at
`localhost:<local port>` — a
browser for a dev server, a Postgres client for a database. The traffic
travels inside the SSH connection to your server, which then connects to the
remote host:port.

## Mosh and forwarding

Forwarding rules ride the SSH connection. With the **mosh** transport:

- **auto-tmux** and **named tmux** launch modes keep an SSH side channel for
  tmux, and forwarding works over it.
- **custom** launch mode has no SSH connection to carry forwards, so adding
  rules is disabled — switch the launch mode to auto-tmux or named tmux.

## Limits

- Local port must be **≥ 1024** (iOS sandbox).
- No duplicate local ports per host.
- Forwarding is local-to-remote only; there's no remote (-R) forwarding.