Query and LAN Discovery

Query and LAN Discovery

Players find servers in the game's multiplayer browser. It has four tabs: Internet (the project's server list, see The Server List), LAN (servers on the same network), Favourites and Recent. Players can also connect directly by address, or through an avalanche://connect/host:port link.

The query is on by default: it follows public, because the server list checks a listed server's query. LAN discovery is off by default. Both are set in [discovery] (Server Configuration). Everything a server tells the browser comes from the same data as its /info, so the tabs never disagree.

The query (query = true)

The browser pings each server it lists on UDP port + 1 (27451 by default) for its player count, mode and ping. The server answers only a request of the exact expected size, never with more bytes than it received, and only after a challenge that proves the asker receives at its address. At most 5 datagrams per 6 seconds per address; the answer is cached for 10 seconds.

The server list does not list a server without the query.

LAN discovery (lan = true)

The LAN tab broadcasts a probe on UDP port 35450. The server answers with its game port, only to hosts on one of its own network links (never to the Internet), at most 5 times per 6 seconds per address. Several servers on one machine all answer. LAN discovery is IPv4 broadcast; in Docker it needs the host's network.

What players see

See Joining a Server.