The master list at mafiam.com/servers collects the servers that are online right now. It stores nothing beyond what a server itself answers to the launcher’s query: name, player count, game edition, season, tags and protocol version.

How a server gets on the list

By itself. m2o_server sends POST /api/announce with its port every minute. This is on by default, see [master] below.
By address. Anyone can enter IP:port in the form on the Servers page.

Either way the master list sends that address the same UDP query the launcher uses (M2OQ + a token) and waits up to two seconds for M2OI. If the server answers, it is listed. From then on the master list polls it every 30 seconds.

A server is online if it answered within the last 150 seconds.
A server that has not answered for 7 days is removed.
It needs a public IPv4 address and an open UDP port. LAN addresses (192.168.x.x, 10.x.x.x) are not accepted.

Settings in m2o_server.ini

[master]
enabled=on           ; off: not on the public list (LAN, testing)
;host=my.domain.com  ; when players reach the server by another address (playit.gg, a domain)

On the command line: --master on|off. The console shows [master] on the public server list as … once the server is listed, otherwise the reason it is not.

POST/api/announce

Registration and heartbeat. The body is JSON (Content-Type: application/json) or a regular form.

Field	Type	Description
`port`	`number`	The server’s game port, the same as in `m2o_server.ini`.
`host`	`string`	Optional. IPv4 or domain players use to reach the server. Without it, the IP the request came from is used. Needed for tunnels like playit.gg and for machines on IPv6.

Send it to master.mafiam.com: that host has only an IPv4 address, so the request always arrives from the IPv4 address players will use, even on a machine with IPv6. mafiam.com answers too, but over IPv6 it needs host.

curl -X POST https://master.mafiam.com/api/announce \
     -H "Content-Type: application/json" \
     -d '{"port": 27015}'

Responses

Code	error	Meaning
`200`		The server answered and is listed. The response carries `server` and `interval`: seconds until the next announce.
`202`		Accepted, but the server did not answer right away (`pending: true`). The master list checks it again within 30 seconds.
`400`	`bad_port`, `bad_host`, `private_ip`, `ipv6`	Bad port, a domain without IPv4, a LAN address, or the request came over IPv6 without `host`.
`422`	`no_answer`	`host` was given, but the server did not answer there. Check that the UDP port is open.
`429`	`rate_limit`	More than 20 requests a minute from one IP.

{
  "ok": true,
  "server": {
    "address": "203.0.113.7:27015",
    "name": "MafiaM server",
    "players": 3,
    "maxPlayers": 128,
    "edition": "de",
    "season": "summer",
    "tags": ["RP", "Cars", "Mafia"],
    "protocol": 26,
    "online": true
  },
  "interval": 60
}

If you write your own announcer: the master list queries the server during the request, so do not block the thread that runs enet_host_service while waiting for the answer. m2o_server announces from a separate thread.

GET/api/servers

Servers online, most players first. Served with Access-Control-Allow-Origin: * and cached for 10 seconds. The launcher’s Internet tab takes its addresses from here and measures ping to each server itself with the same M2OQ.

Parameter	Description
`all=1`	Also return servers seen in the last 7 days (`online: false`).
`edition=de`	Definitive Edition only, `classic` for Classic only.

{
  "ok": true,
  "updated": 1792351200,
  "online": 1,
  "players": 3,
  "protocol": 26,
  "servers": [
    {
      "address": "203.0.113.7:27015",
      "host": "203.0.113.7",
      "ip": "203.0.113.7",
      "port": 27015,
      "name": "MafiaM server",
      "players": 3,
      "maxPlayers": 128,
      "edition": "de",
      "season": "summer",
      "tags": ["RP", "Cars", "Mafia"],
      "protocol": 26,
      "online": true,
      "lastSeen": 1792351190,
      "firstSeen": 1792340000
    }
  ]
}

Field	Description
`address`	What to enter in the launcher: `host:port`. If the server registered with a domain, the domain is here.
`edition`	`de` or `classic`.
`season`	`summer` (1950s) or `winter` (1940s).
`tags`	From `[server] tags` in m2o_server.ini, up to 8.
`protocol`	The server’s protocol version. A launcher with another version cannot join it. The top-level `protocol` is the newest one among online servers.
`lastSeen`	Unix time of the last answer.

GET/api/servers/{host:port}

One server by address, for example /api/servers/203.0.113.7:27015. Unknown servers return 404 with error: not_found.

GET/api/downloads

The files on the Download page: link, size, date and sha256.

{
  "ok": true,
  "files": {
    "client": {
      "name": "m2o-client.zip",
      "available": true,
      "url": "https://mafiam.com/files/m2o-client.zip",
      "size": 199229440,
      "updated": 1792351200,
      "sha256": "…"
    },
    "server": { "name": "m2o-server.zip", "available": false }
  }
}

Master list and API