# Server topology

Companion diagram + port table for `docs/server-runtime.md`. Describes the
*intended* production layout of the Debian VPS m2 stack. What is live today is
only a subset (see the runtime audit for the actual state).

## ASCII diagram

```
                          ┌─────────────────────────────┐
                          │          Players            │
                          │  (Metin2.exe + launcher)    │
                          └──────────────┬──────────────┘
                                         │  TCP (11000 auth, 11011..11013
                                         │        channel1, 11991 channel99)
                                         ▼
    ════════════════════════════ mt2.jakubkadlec.dev ════════════════════════════
    ║                                                                           ║
    ║   ┌──────────────────┐      ┌──────────────────┐      ┌────────────────┐ ║
    ║   │   metin-auth     │      │ metin-game@ch1_c1│      │ metin-game@    │ ║
    ║   │   (game_auth)    │ p2p  │ (channel1_core1) │ p2p  │ ch99_c1        │ ║
    ║   │  :11000 client   │◄────►│  :11011 client   │◄────►│  :11991 client │ ║
    ║   │  :12000 p2p      │      │  :12011 p2p      │      │  :12991 p2p    │ ║
    ║   └────────┬─────────┘      └────────┬─────────┘      └────────┬───────┘ ║
    ║            │                         │  metin-game@ch1_c2/c3  │         ║
    ║            │                         │ :11012/12012 :11013/12013         ║
    ║            │                         │                         │         ║
    ║            │   DB proxy/cache layer  │                         │         ║
    ║            └────────────┐  ┌─────────┴─────────────┐  ┌────────┘         ║
    ║                         ▼  ▼                       ▼  ▼                  ║
    ║                      ┌──────────────────────────────────┐                ║
    ║                      │          metin-db (db)           │                ║
    ║                      │       bind 0.0.0.0:9000          │                ║
    ║                      │  (gated by metin-db-ready.svc)   │                ║
    ║                      └──────────────┬───────────────────┘                ║
    ║                                     │  SQL                               ║
    ║                                     ▼                                    ║
    ║                      ┌──────────────────────────────────┐                ║
    ║                      │       mariadbd 11.8.6            │                ║
    ║                      │  127.0.0.1:3306                  │                ║
    ║                      │  DBs: account, player, common,   │                ║
    ║                      │       log, hotbackup             │                ║
    ║                      └──────────────────────────────────┘                ║
    ║                                                                           ║
    ║   systemd orchestration:                                                  ║
    ║     metin-server.service (oneshot umbrella, PartOf everything)            ║
    ║       ├─ Requires mariadb.service                                         ║
    ║       └─ metin-db → metin-db-ready → metin-auth + metin-game@<instance>   ║
    ║                                                                           ║
    ║   Secrets:                                                                ║
    ║     /etc/metin/metin.env  (root:root 600, EnvironmentFile= for all units) ║
    ║                                                                           ║
    ════════════════════════════════════════════════════════════════════════════
```

## Process / port table

| Process name     | systemd unit                          | Client port | P2P port | Binds to   | Role                                                  | Config file                                           |
| ---------------- | ------------------------------------- | ----------- | -------- | ---------- | ----------------------------------------------------- | ----------------------------------------------------- |
| `db`             | `metin-db.service`                    | 9000        | —        | `0.0.0.0`  | DB proxy/cache; talks to MariaDB, serves auth+game    | `share/conf/db.txt` (+ `/etc/metin/metin.env`)        |
| `game_auth`      | `metin-auth.service`                  | 11000       | 12000    | (default)  | account login, token handoff to channels              | `channels/auth/CONFIG`                                |
| `channel1_core1` | `metin-game@channel1_core1.service`   | 11011       | 12011    | (default)  | ch1 core1, MAP_ALLOW 1 4 5 6 3 23 43 112 107 67 68 72 208 302 304 | `channels/channel1/core1/CONFIG`          |
| `channel1_core2` | `metin-game@channel1_core2.service`   | 11012       | 12012    | (default)  | ch1 core2, same channel different core                | `channels/channel1/core2/CONFIG`                      |
| `channel1_core3` | `metin-game@channel1_core3.service`   | 11013       | 12013    | (default)  | ch1 core3                                             | `channels/channel1/core3/CONFIG`                      |
| `channel99_core1`| `metin-game@channel99_core1.service`  | 11991       | 12991    | (default)  | ch99 core1, event/test channel. MAP_ALLOW 113 81 100 101 103 105 110 111 114 118 119 120 121 122 123 124 125 126 127 128 181 182 183 200 | `channels/channel99/core1/CONFIG` |
| `mariadbd`       | `mariadb.service` (distro pkg)        | 3306        | —        | `127.0.0.1`| relational store                                      | `/etc/mysql/mariadb.conf.d/*`                         |

Supporting, not a process:

| Unit                       | Type    | Purpose                                                          |
| -------------------------- | ------- | ---------------------------------------------------------------- |
| `metin-server.service`     | oneshot | umbrella. Restarting it cycles all sub-units via `PartOf=`.      |
| `metin-db-ready.service`   | oneshot | `metin-wait-port 127.0.0.1 9000 30` — gates auth+game on db up.  |

## Data flow

1. Player connects to `mt2.jakubkadlec.dev:11000` (auth).
2. `game_auth` authenticates against `account` via `db` (`127.0.0.1:9000`)
   which proxies to MariaDB.
3. `game_auth` hands the player a token and the channel pick.
4. Player connects to e.g. `:11011` (channel1 core1). The core reads player
   state via `db` from `player` + `common`, loads maps per `MAP_ALLOW` and
   quest binaries from `share/locale/`.
5. Cross-core traffic (channel switch, whisper, guild) uses the P2P ports
   (`12000`, `12011`..`12013`, `12991`) on loopback.
6. `db` persists to MariaDB asynchronously (`AsyncSQL` pools, batch-writes
   at `SAVE_EVENT_SECOND_CYCLE=180`s from `game.txt`).
7. `log` DB receives audit/event rows (item trades, combat, etc.) through
   a dedicated `AsyncSQL` connection.