server/README.md

# The Metin2 Server
The Old Metin2 Project aims at improving and maintaining the 2014 Metin2 game
files up to modern standards. The goal is to archive the game as it was in order
to preserve it for the future and enable nostalgic players to have a good time.

For-profit usage of this material is certainly illegal without the proper
licensing agreements and is hereby discouraged (not legal advice). Even so, the
nature of this project is HIGHLY EXPERIMENTAL - bugs are to be expected for now.

## 1. Usage
We aim to provide Docker images which _just work_ for your convenience.
A Docker Compose project is maintained in the [Deployment project](https://git.old-metin2.com/metin2/deploy).
Please head over there for further instructions.

## 2. Building
### A. Building Docker images
#### Building a Docker image from the repository
In order to build a local Docker image on your local architecture, just build the
provided Dockerfile in this project:

```shell
docker build -t metin2/server:test --provenance=false .
```

#### Publishing a multiplatform Docker image manually
This command is reserved only for repository maintainers in order to publish
new Docker images for public use with the Deployment project.

**WARNING:** Using WSL for building might lead to QEMU segmentation fault issues;
this can be worked around by using `binfmt` and `qemu-user-static` as described 
[here](https://github.com/docker/buildx/issues/1170#issuecomment-1159350550).

```shell
docker build --push -t git.old-metin2.com/metin2/server:<IMAGE-TAG-HERE> --platform linux/amd64,linux/arm64 --provenance=false .
```

### B. Building the binaries yourself (for advanced users)
_Sadly, we're unable to provide hand-holding services. You should have some C++ development experience
going forward with this route._

A Linux environment is strongly recommended, preferably of the Ubuntu/Debian
variety. This project is also compatible with WSL, even though WSL can be buggy
at times. FreeBSD/Windows compatibility is untested and unsupported for the
time being - there are other projects out there if that's what you want.

#### Setting up the requirements
On your Linux box, install the dependencies for `vcpkg` and the other libraries
we're going to install.
```shell
apt-get update
apt-get install -y git cmake build-essential tar curl zip unzip pkg-config autoconf python3 libncurses5-dev
```

Also install DevIL (1.7.8) and the BSD compatibility library:
```shell
apt-get install -y libdevil-dev libbsd-dev
```

Install `vcpkg` according to the [latest instructions](https://vcpkg.io/en/getting-started.html).

Build and install the required libraries:
```shell
vcpkg install cryptopp effolkronium-random libmariadb libevent lzo fmt spdlog argon2
```

#### Building the binaries
Instead of building the binaries directly from the CLI, we recommend using an IDE, since
you're probably doing some kind of development anyway. See the "Development" section for more information on that.

If you decide do build from the command line, make sure to find the right path for `vcpkg.cmake` and run the following:
```shell
mkdir build/
cd build && cmake -DCMAKE_TOOLCHAIN_FILE=/path/to/vcpkg/scripts/buildsystems/vcpkg.cmake ..
make -j $(nproc)
```

If everything goes right, you should now have compiled binaries in the `build/` directory.

## 2. Development
The preferred IDE in order to develop and debug the server is [CLion](https://www.jetbrains.com/clion/),
baked by the fine Czech folks at JetBrains. Educational licenses are available if you're elligible.

1. Make sure you install all the dependencies mentioned in the "Build the binaries yourself" section.
2. Inside a WSL environment, a remote SSH one or directly on a Linux machine, just
clone this repository and open it with CLion.
3. Set up "Run/Debug Configurations" of the "CMake Application" type for
the `db`, `auth`, and `game` services, using the "db" target for the former and
the "game" target for the latter two. Make sure each service has its own working
directory with all the required configuration and game files.
4. Optionally, add a "Compound" configuration containing these three configurations
in order to start them at once.
5. Of course, you'll need a MySQL 5.x database, Valgrind and any other development
goodies you wish. Also, a lot of time.

## 3. Improvements
### Major improvements
- The binaries run on 64-bit Linux with the network stack being partially rewritten in Libevent.
- CMake build system mainly based on `vcpkg`. Docker-friendly architectural approach.
- HackShield and other proprietary binaries were successfully _yeeted_, the project only has open-source dependencies.
- Included gamefiles from [TMP4's server files](https://metin2.dev/topic/27610-40250-reference-serverfile-client-src-15-available-languages/) (2023.08.05 version).

### Minor improvements
- Removed unused functionalities (time bombs, activation servers, other Korean stuff)
- Switched to the [effolkronium/random PRNG](https://github.com/effolkronium/random) instead of the standard C functions.
- Refactored macros to modern C++ functions.
- Network settings are manually configurable through the `PUBLIC_IP`, `PUBLIC_BIND_IP`, `INTERNAL_IP`, `INTERNAL_BIND_IP` settings in the `game.conf` file. (Might need further work)
- Refactored logging to use [spdlog](https://github.com/gabime/spdlog) for more consistent function calls.
- Refactored login code to use Argon2ID.

## 4. Bugfixes
**WARNING: This project is based on the "kraizy" leak. That was over 10 years ago.
A lot of exploits and bugs were discovered since then. Most of these public bugs are UNPATCHED.
This is a very serious security risk and one of the reasons this project is still experimental.**

### Gameplay
- Fixed invisibility bug on login/respawn/teleport etc.
- Fixed player level not updating [(thread)](https://metin2.dev/topic/30612-official-level-update-fix-reversed/)

### Exploits
- See the warning above :(

### Architectural
- Fixed various bugs caused by the migration of the codebase to 64-bit (some C/C++ data types have different lengths based on the CPU architecture)
- Fixed buffer overruns and hardcoded limits in the MAP_ALLOW parsing routines.
- Fixed quest server timers cancellation bug which could cause a server crash - [(thread)](https://metin2.dev/topic/25142-core-crash-when-cancelling-server-timers/).
- Fixed buffer overruns and integer overflows in SQL queries.

## 5. Further plans
- Migrate `db.conf` and `game.conf` to a modern dotenv-like format, which would enable pretty nice Docker images.
- Use the [fmt](https://fmt.dev/latest/index.html) library for safe and modern string formatting.
- Handle kernel signals (SIGTERM, SIGHUP etc.) for gracefully shutting down the game server.
- Improve memory safety.
- Use fixed width integer types instead of Microsoft-style typedefs.
- Convert C-style strings to C++ `std::string`.
- Perform static and runtime analysis.
- Find and implement other fitting improvements from projects such as [Vanilla's core](https://metin2.dev/topic/14770-vanilla-core-latest-r71480/), [TMP's serverfiles](https://metin2.dev/topic/27610-40250-reference-serverfile-client-src-15-available-languages/).
- Find time to take care of this project.