Add --interface option to bind to a specific network interface

[Copilot]

Users on multi-homed machines (e.g., a home server acting as a LAN router) have no way to prevent Sendspin from being accessible on all interfaces, including WAN-facing ones. This adds a --interface <IP> option to restrict mDNS discovery and daemon listener binding to a single interface.

Changes

• settings.py: Added interface: str | None to ClientSettings with full load/save/update support.
• discovery.py: ServiceDiscovery accepts interfaces: list[str] | None; passes it to AsyncZeroconf to restrict mDNS to that interface. Same parameter threaded through discover_servers() and discover_clients().
• cli.py: --interface added to both TUI player and daemon argument parsers; settings default applied; passed through to AppArgs / DaemonArgs.
• tui/app.py: AppArgs gains interface; SendspinApp passes [interface] to ServiceDiscovery.
• daemon/daemon.py: DaemonArgs gains interface; server-initiated listener uses host=interface (falls back to 0.0.0.0) so the aiohttp server only binds on that IP.
• README.md: New "Network Interface Binding" section; interface added to settings table and example config.

Usage

# Restrict TUI mDNS discovery to LAN interface
sendspin --interface 192.168.1.5

# Restrict daemon listener and mDNS to LAN interface only
sendspin daemon --interface 192.168.1.5

Can also be persisted in ~/.config/sendspin/settings-daemon.json:

{ "interface": "192.168.1.5" }

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• python-zeroconf.readthedocs.io
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[balloob]

@copilot move this to bottom of option descriptions ni README, it is not important

[Copilot]

Done in 404586e — moved the "Network Interface Binding" section to just before the "Install as Daemon" heading.

[Copilot]

Pull request overview

Adds a new --interface <IP> option (and corresponding persisted setting) to restrict Sendspin’s network behavior on multi-homed machines, primarily to avoid exposing discovery/listeners on unintended interfaces.

Changes:

• Introduces interface: str | None in ClientSettings and loads it from the settings JSON.
• Threads an optional interfaces list through mDNS discovery (ServiceDiscovery, discover_servers(), discover_clients()) and uses it when creating AsyncZeroconf.
• Adds --interface to the player and daemon CLIs, passes it through AppArgs/DaemonArgs, and binds the daemon’s server-initiated listener to that address.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
sendspin/tui/app.py	Passes a single interface (when configured) into ServiceDiscovery for mDNS discovery scoping.
sendspin/settings.py	Adds persisted interface setting and loads it from JSON.
sendspin/discovery.py	Adds interface scoping support to ServiceDiscovery, discover_servers(), and discover_clients() via AsyncZeroconf(interfaces=...).
sendspin/daemon/daemon.py	Binds the server-initiated listener to the configured interface (else 0.0.0.0).
sendspin/cli.py	Adds --interface for player + daemon, applies settings defaults, and passes through to args structs.
README.md	Documents the new interface setting and adds a “Network Interface Binding” section.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

args.interface is accepted from both CLI and persisted settings, but it's never validated. If a user provides an invalid IP (or a hostname/interface name that aiohttp/zeroconf can't bind to), this can raise an OSError during listener startup and currently bubbles up to an unhandled exception in main(). Consider validating --interface early (e.g., with ipaddress.ip_address) and turning failures into a CLIError with a clear message.

[Copilot]

The new interfaces parameter is documented as accepting "IP addresses or interface names", but the CLI/README describe --interface as an IP address only. Please align the documentation and supported inputs (either document/validate interface names everywhere, or narrow this docstring to IP addresses) so users know what is actually supported.

Suggested change

	interfaces: Optional list of IP addresses or interface names to restrict
	mDNS discovery to. If None, all interfaces are used.
	interfaces: Optional list of IP addresses to restrict mDNS
	discovery to. If None, all interfaces are used.

[Copilot]

ClientSettings now persists an interface field, but there isn't corresponding unit coverage. Since there are already tests asserting settings load behavior for other fields, it would be good to add a small test that writes {"interface": "192.168.1.5"} and asserts it is loaded (and/or that to_dict() includes it on save).

[Copilot]

The daemon subcommand's --interface help text says it "also restricts mDNS discovery", but the daemon code path doesn't use ServiceDiscovery/discover_*() at all. As implemented, --interface only affects the incoming listener bind address (and is ignored in client-initiated mode). Please adjust the help text to match the actual behavior to avoid misleading users.

Suggested change

	"interface only. Also restricts mDNS discovery to this interface. "
	"interface only. Ignored in client-initiated mode (--url). "