# How-To: `pos network`

Networking day-to-day: IP/diagnostic info, Wi-Fi hotspots, host discovery, and
port checks. Tools: `ip`, `hotspot`, `scan`, `checkport`.

| Tool | What it does |
|------|--------------|
| `pos network ip` | Interfaces, default route, public IP + location |
| `pos network hotspot` | Wi-Fi AP via `create_ap` / `wihotspot-gui` |
| `pos network scan` | Two-phase host discovery with `nmap` |
| `pos network checkport` | Is a TCP port open on a host? |

---

## `pos network ip` — where am I, what's my IP

```bash
pos network ip
```

Shows local interfaces + addresses, the default route, and your public IP with
its geolocation. Useful before `ssh`-ing home or opening ports.

**Recipe:** public IP on the go — this is the same value the health digest
includes, so if your home IP changed you'll see it in the 08:00 report.

**Troubleshooting:** the public-IP lookup needs outbound HTTPS; if it prints
"unreachable"/location unknown, your network or a firewall is blocking
`api.ipify.org` / the geo provider.

---

## `pos network hotspot` — turn the machine into a Wi-Fi AP

Requires the precompiled `create_ap` + `wihotspot-gui` binaries shipped in
`x64_bin/` (or `arm64_bin/`) and installed to `/usr/local/bin` by `install.sh`.
The GUI needs a desktop session; the CLI needs a wireless NIC in AP mode.

```bash
pos network hotspot                       # launch the wihotspot-gui
pos network hotspot start wlan0 eth0 MyNet mypass      # AP on wlan0, internet via eth0
pos network hotspot start --foreground wlan0 eth0 MyNet mypass   # block until Ctrl+C
pos network hotspot stop                  # stop the running AP (auto-detected)
pos network hotspot stop wlan0            # stop by interface/PID
pos network hotspot status                # list running APs
```

Positional args: `<wifi-iface> [<internet-iface>] <ssid> [<passphrase>]`.
Without `--foreground`, it asks whether to run in the background; daemonized APs
log to `/var/log/linux_post_install_hotspot.log`.

**Recipes:**
- Give guests internet while tethered: `pos network hotspot start wlan0 eth0 GuestNet secret`.
- After starting, find who joined with `pos network scan 192.168.42.0/24` (create_ap
  default subnet) or `pos network checkport <phone-ip>:80`.

**Troubleshooting:**
- `create_ap` not found → the precompiled binary wasn't installed; re-run
  `./install.sh` (Phase 2 copies `x64_bin/` → `/usr/local/bin`).
- "No suitable AP mode" → your Wi-Fi card/driver doesn't support AP mode; use the
  GUI (wihotspot-gui) or a USB dongle.
- Client has IP but no internet → check the `<internet-iface>` arg / NAT
  forwarding; `create_ap --daemon` logs to the hotspot logfile.

---

## `pos network scan` — find hosts on the LAN

Requires `nmap` (`sudo apt install nmap`).

```bash
pos network scan 192.168.1.0/24          # fast discovery
pos network scan 10.0.0.0/28 --full      # + OS, ports, services, NSE scripts
pos network scan 172.1.1.104             # single host
pos network scan 192.168.1.0/24 --retries 3
```

Two phases: fast ping-sweep discovery, then — only with `--full` — a detailed
metadata scan on the alive hosts.

**Recipe:** after `pos network hotspot start`, find attached clients:
`pos network scan 192.168.42.0/24`.

**Troubleshooting:** `nmap` missing → install it. Scanning a remote/hostile
network without permission is not advisable; `--full` is slow — scope it to a
`/24` or a single host.

---

## `pos network checkport` — is a port open?

```bash
pos network checkport 192.168.1.1:80
pos network checkport 10.0.0.5:443
```

Exits non-zero if the port is closed/unreachable, so you can chain it:

**Recipe:** confirm a self-hosted service is up before alerting:
```bash
pos network checkport jellyfin.local:8096 && notify_send "Jellyfin reachable" \
  || notify_send "Jellyfin DOWN"
```
(see [communication](communication.md) for `notify_send`).

**Troubleshooting:** a "closed" answer from a host that *is* up usually means a
local firewall — check `sudo pos system firewall` rules and service binds
(`ss -tlnp`).

---

## Related

- Reference tables: [DOC/POS.md → network](../POS.md)
- Firewall that may block these: [system.md](system.md)
- Public IP in the daily digest: [system.md → health](system.md)