LANCommander.Plugins.Relay 1.0.0

LANCommander Relay

A LANCommander server plugin that hosts the Interposer's network relay. When enabled, games running under Interposer can connect to the relay to play over the network. It works by hooking standard Windows networking APIs linking your game to other players without the requirement of a standard VPN.

How players connect

The LANCommander launcher on Windows does it by itself. When a player starts a game that has a LAN multiplayer mode over TCP/IP or IPX, the launcher:

1. asks this plugin for a relay session (POST /api/Plugins/Relay/Sessions, as the signed-in player);
2. gets back where the relay listens, the game's relay network, and a ticket;
3. starts the game under the Interposer with those settings, injecting it or, for a game that already carries the Interposer as a proxy DLL, handing them to the proxy. 32-bit and 64-bit games both work.

Everyone playing the same game lands in the same network, one per game, and sees each other's sessions. Players can turn the relay off with NetworkRelay.Enabled: false in the launcher's Settings.yml.

What it adds

Settings → Relay (/Plugins/Relay), administrators only:

• Overview: whether the relay is listening, uptime, players connected, networks, peak players, sessions, refusals and traffic. Below that, the connected players (the game, its network, virtual address, where they connect from, UDP or TCP path, traffic, how long they have been connected, the LANCommander account they signed in as) with a button to disconnect each one. Then a log of the relay's recent activity: starts, joins, departures, refusals and errors. The page updates live.

• Settings:

  • Enabled: the relay is off until an administrator turns it on.
  • Port: the TCP port games connect to, and the UDP port datagrams use. Default 41300.
  • Use UDP: turn off where the UDP port cannot be opened; everything then travels over TCP.
  • Require sign-in: see Authentication. On by default.
  • Players per network.
  • Public address: the host games connect to, when it is not the one the launcher reaches the server at, such as behind a reverse proxy that only carries HTTP.

  Saving restarts the relay. Connected games reconnect by themselves and ask for their old virtual addresses back.

API: POST /api/Plugins/Relay/Sessions, for any signed-in user, through LANCommander's plugin endpoint support. It returns 503 while the relay is not running.

Settings and the ticket signing key are stored in PluginData/Relay/ under the server's data directory. The activity log is kept in memory (the latest 500 entries); everything also goes to the server's own log.

Authentication

With Require sign-in on, the relay only admits a game that presents a relay ticket this server issued. The launcher gets one per launch from the sessions endpoint, as the signed-in player. A ticket:

• is signed (HMAC-SHA256) with a key only this server has, kept in PluginData/Relay/ticket.key. Deleting the key and restarting the server revokes every ticket issued so far;
• names the player's account and one network, the game's, and the relay puts the game there whatever network it asked for;
• expires after 24 hours, long enough for a session, since the Interposer reconnects with the ticket it started with;
• is good for nothing but the relay. It is not the player's access token, so one seen on the wire cannot be used against the server's API.

Relay traffic, ticket included, is not encrypted. Anyone who can watch a player's traffic could reuse their ticket to join that game's network, as them, until it expires.

With sign-in not required, anyone who can reach the port may join, into any network. A game with a valid ticket is still placed in its ticket's network and shown under its account.

A ticket is checked when a game connects, including each reconnect, so a player removed from the server can rejoin until their ticket expires. Disconnect drops a game, but it reconnects with the same ticket; to shut everyone out at once, delete the key and restart the server.

Installing

On a LANCommander server (2.2.0 or later), open Settings → Plugins. Find Relay on the Browse tab and install it, or download the .nupkg attached to a release and upload it on the Installed tab. The plugin is installed when the server restarts.

Hosting notes

• Open the relay port for both TCP and UDP in the server's firewall, and forward both if players connect from outside your network. In Docker, publish both: -p 41300:41300/tcp -p 41300:41300/udp.
• Every network hands out addresses from 10.13.37.0/24; networks are isolated from each other.