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https://github.com/beverly-hills-money-gangster/daikombat-server

Daikombat game online server
https://github.com/beverly-hills-money-gangster/daikombat-server

doom fps-game game-server gamedev java java-game-development java-shooter-game libgdx-game netcode netty netty-server protobuf tcp

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Daikombat game online server

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# Daikombat Server [![](https://jitpack.io/v/beverly-hills-money-gangster/Daikombat-server.svg)](https://jitpack.io/#beverly-hills-money-gangster/Daikombat-server) [![](https://snyk.io/test/github/beverly-hills-money-gangster/Daikombat-server/badge.svg)](https://snyk.io/test/github/beverly-hills-money-gangster/Daikombat-server)



Daikombat Server is the server code repository for a simple Doom-like online shooter game with a non-stop death-match mode. It is built using Maven, Netty, Spring, and Java 14.

Client/desktop code is also publicly available on [GitHub](https://github.com/beverly-hills-money-gangster/DaikombatDesktop).

 

## Prerequisites



- Java 14

- Maven 3.6.3



## Architecture overview



The server opens a TCP connection and serves in-game events as protobuf messages(find `.proto` schema in `schema` module). 

The client publishes game commands and then subscribes to server events by collecting them in an in-memory queue that is meant to be polled during game rendering. 

All communications (server-to-client and client-to-server) are totally non-blocking.



### Known issues



- TCP is a bad choice for fast-paced online shooter games due to head-of-line blocking. In the future, the protocol is likely to be changed to either UDP or QUIC.

- The server is totally not scalable at this moment. High availability and load balancing are not provided.

- The server is NOT authoritative

- Basic anti-cheat



## Configuration



Game server can be configured using the following environment variables:



- `GAME_SERVER_PORT`  TCP server port at which client connections are going to be accepted. Default - `7777`.

- `GAME_SERVER_GAMES_TO_CREATE` Games to create. Default - `10`.

- `GAME_SERVER_MAX_PLAYERS_PER_GAME` Maximum number of players to join a game. Default - `25`. Total number of players on the server is `GAME_SERVER_GAMES_TO_CREATE*GAME_SERVER_MAX_PLAYERS_PER_GAME`.

- `GAME_SERVER_MOVES_UPDATE_FREQUENCY_MLS` Frequency(in milliseconds) at which server notifies players about other players' positioning on the map. Default - `50`.

- `GAME_SERVER_MAX_IDLE_TIME_MLS` Maximum idle time(in milliseconds) for a player. "Idle" - no network activity, which includes in-game events + ping responds. For example, if player connects to a game and doesn't move but responds to PING requests, then it's NOT considered idle. This check is mostly needed when a TCP connection was closed abruptly(no FIN). Default - `10_000`.

- `GAME_SERVER_DEFAULT_SHOTGUN_DAMAGE` Gunshot damage. Default - `20`.

- `GAME_SERVER_DEFAULT_RAILGUN_DAMAGE` Railgun damage. Default - `75`.

- `GAME_SERVER_DEFAULT_PUNCH_DAMAGE` Punch damage. Default - `50`.

- `GAME_SERVER_DEFAULT_MINIGUN_DAMAGE` Minigun damage. Default - `5`.

- `GAME_SERVER_FAST_TCP` Enables fast TCP configurations(used mostly for testing, not recommended to be set to `false` in prod). Default - `true`.

- `GAME_SERVER_FRAGS_PER_GAME` Frags to win a game. Default - `25`.

- `GAME_SERVER_QUAD_DAMAGE_SPAWN_MLS` Time (in millisecond) it takes to spawn a quad damage power-up orb. Default - `45_000`.

- `GAME_SERVER_QUAD_DAMAGE_LASTS_FOR_MLS` Time (in millisecond) quad damage lasts for. Default - `10_000`.

- `GAME_SERVER_DEFENCE_SPAWN_MLS` Time (in millisecond) it takes to spawn a defence power-up orb. Default - `35_000`.

- `GAME_SERVER_DEFENCE_LASTS_FOR_MLS` Time (in millisecond) defence lasts for. Default - `10_000`.

- `GAME_SERVER_INVISIBILITY_SPAWN_MLS` Time (in millisecond) it takes to spawn an invisibility power-up orb. Default - `30_000`.

- `GAME_SERVER_INVISIBILITY_LASTS_FOR_MLS` Time (in millisecond) invisibility lasts for. Default - `15_000`.

- `GAME_SERVER_POWER_UPS_ENABLED` Turns power-ups on and off. Default - `true`.

- `GAME_SERVER_TELEPORTS_ENABLED` Turns teleports on and off. Default - `true`.

- `GAME_SERVER_PLAYER_SPEED` Player speed. Default - `5`.

- `GAME_SERVER_PLAYER_STATS_TIMEOUT_MLS` Time (in milliseconds) to store player's stats for connection recovery. Default - `120000`.

- `GAME_SERVER_PLAYER_SPEED_CHECK_FREQUENCY_MLS` Frequency(in milliseconds) at which server checks all players' speed. Anybody moving faster than `GAME_SERVER_PLAYER_SPEED` will be kicked-out. Default - `10_000`

- `SENTRY_DSN` Sentry DSN. Not specified by default.



Game client is also configurable through environments variables:



- `CLIENT_MAX_SERVER_INACTIVE_MLS` Maximum server inactivity time(in milliseconds). Default - `10_000`.

- `CLIENT_FAST_TCP` Enables fast TCP configurations(used mostly for testing, not recommended to be set to `false` in prod). Default - `true`.



Note: all default (both client and server) configurations are production-ready.



## Deployment and integration



### Game client integration

All submodules, including network client, can be used as maven/gradle dependencies using [jitpack](https://jitpack.io/#beverly-hills-money-gangster/Daikombat-server).



### Docker



Server image is deployed on every release to [Github container registry](https://ghcr.io/beverly-hills-money-gangster/daikombat_server).

A sample [docker-compose file](/docker-compose.yaml) can be found in the root folder.



## Monitoring



### Server monitoring



#### JVM metrics



Server JVM metrics can be monitored through JMX remotely. See [docker-compose file](/docker-compose.yaml). 

In the sample, JMX agent is running on port 9999 listening to incoming connections initiated by 127.0.0.1. 

If server is running in the cloud, then it's possible to port-forward JMX using the following command:



```

ssh -L 9999:127.0.0.1:9999 @

```



#### Heap dumps



Apart from JMX metrics, the server is configured to drop a heap dump file on out-of-memory.



#### Micrometer



All command handlers publish Micrometer timer metrics through JMX. See "metrics" in Jconsole "MBeans" tab.



#### Sentry



All errors are automatically published to Sentry. See `SENTRY_DSN` env var.



### Client monitoring



`GameConnection.java` has `networkStats` field that gathers basic network stats including:

- ping (and also 50th, 75th, and 99th percentiles)

- number of sent protobuf messages

- number of received protobuf messages

- total protobuf outbound payload size

- total protobuf inbound payload size



## Development



### Handy Maven commands



Here are some commands that might be useful while coding.



#### Update all submodules' versions

```

mvn versions:set -DnewVersion=

```



#### Run static code analysis

```

mvn spotbugs:check 

```



#### Update protobuf schema



```

rm .\schema\src\main\java\com\beverly\hills\money\gang\proto\* 

protoc --java_out=./schema/src/main/java/ .\schema\src\main\resources\server-response.proto

protoc --java_out=./schema/src/main/java/ .\schema\src\main\resources\server-command.proto

```



### Testing and QA



The project provides good quality of service by:

- Unit and integration testing (Junit). Minimum coverage requirements can be found in Jacoco configs.

- Static code analysis (Spotbugs)

- Dependency check (Snyk)

- Resiliency testing (ToxiProxy)

- Load testing. See `com.beverly.hills.money.gang.bots.BotRunner` for spawning dummy bots

- Game client manual acceptance testing is also involved in the process. Dev mode is provided for the desktop version.