slpcli

🚀 A simple C++ tool to query the Server List Ping (SLP) of a Minecraft: Java Edition (Notchian) server.

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🔧 A naive implementation of the Server List Ping (SLP) protocol in C++ using non-boost Asio.

📦 Available on the AUR
      

⭐ Enjoying this repo? A star would mean a lot.

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📌 Usage

./slpcli [OPTIONS] addr [port]


POSITIONALS:
  addr TEXT REQUIRED          Server address with optional ":port".
  port UINT                   Port of the Minecraft server (default 25565).

OPTIONS:
  -h,     --help              Print this help message and exit
  -s,     --silent            Only prints the JSON or an empty string if error.
  -a,     --address TEXT REQUIRED
                              Server address with optional ":port".
  -p,     --port UINT         Port of the Minecraft server (default 25565).
  -t,     --timeout INT       The timeout in seconds at which the query is dropped
          --protocol-version INT
                              The protocol version that the client plans on using to connect to
                              the server. Do not change if you do not know what it means.

🛠️ Examples

🎯 Basic Usage

Without specifying a port (default port 25565):

./slpcli mc.hypixel.net

Specifying a port:

./slpcli 23.230.3.162:25572

Specifying a port (option 2):

./slpcli 23.230.3.162 25572

Real example for Hypixel, prettified with jq:

$ ./slpcli --silent mc.hypixel.net | jq .
{
  "version": {
    "name": "Requires MC 1.8 / 1.21",
    "protocol": 47
  },
  "players": {
    "max": 200000,
    "online": 31198,
    "sample": []
  },
  "description": "                §aHypixel Network §c[1.8-1.21]\n     §6§lSB 0.23.1 §2§lFORAGING §8§l- §e§lSUMMER EVENT",
  "favicon": "<trimmed for GitHub>"
}

Video example:

🔍 Extracting Data with jq

Display the number of online players using jq:

./slpcli -s purpleprison.net | jq '.players.online'
# Output: 438

🖼️ Displaying Server Favicon

Use chained bash commands with feh to display the server favicon:

./slpcli mc.hypixel.net -s | jq .favicon -r | cut -d, -f2 | base64 -d | feh -

Save favicon as an image file:

./slpcli mc.hypixel.net -s | jq .favicon -r | cut -d, -f2 | base64 -d > favicon.png

🤫 Quiet Mode

The -s or --silent option suppresses diagnostic messages, outputting only the raw JSON payload or an empty string upon error. Useful for shell pipelines.

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📦 Installation

Warning

The project is currently only available on Arch Linux's User Repository (AUR). On other distributions and OSes you will have to build it manually or download a binary from the Releases.

You have two main ways to install slpcli on Arch Linux:

1. Use your favorite AUR helper like yay or paru:

yay -S slpcli-git

2. Install directly from the PKGBUILD file:

sudo pacman -S --needed git base-devel
git clone --recursive https://github.com/Urpagin/slpcli.git
cd slpcli/arch-pkg
makepkg -si

🏗️ Building

Use the provided run_debug.sh script or build manually.

Manual Build

mkdir build && cd build
cmake ..
make -j$(nproc)

(To be improved later.)

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💻 Compatibility

Platforms 🌐

Cross platform thanks to Asio

OS	Compatibility
Linux	✅ YES
macOS	✅ YES
Windows	✅ YES

Note

Manual build required on macOS and Windows. On Arch Linux you can use the AUR package.

📐 C++ Version

• Requires C++23 or newer.

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📖 Integrating SLP Code in Your C++ Project

Starting from a basic project structure:

main.cpp

int main() {
    return 0;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.24)
project(myapp)

add_executable(myapp main.cpp)

🚩 Steps

1. 📥 Clone the repository (do not omit --recursive):

git clone --recursive https://github.com/Urpagin/slpcli.git

2. 🔗 Link the library in your project's CMakeLists.txt:

cmake_minimum_required(VERSION 3.24)
project(myapp)

# Include SLP library
add_subdirectory(slpcli/libs/slp)

add_executable(myapp main.cpp)

# Link SLP library
target_link_libraries(myapp PRIVATE slp)

3. 📝 Use the library in your project:

#include <iostream>
#include "slp.h"

int main() {
    auto ping = slp("mc.hypixel.net");
    auto response = ping.query_slp();
    std::cout << response << std::endl;
    return 0;
}

4. 🏭 Build and run:

mkdir -p build && cd build
cmake ..
make -j$(nproc)
./myapp

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⚠️ Known Issues

🔢 VarInt handling

We are storing VarInts as a 32-bit signed integer, however, a VarInt is defined in the protocol with a maximum of 5 bytes, which is 35 bits. I think this means I am not spec-compliant, but with the packets we're handling, I don't think it matters.

TODO

• Remove the small overhead of launching a new thread with std::thread by using an Asio-native solution (see Timeouts) / Source Code. (in progress in the devel branch)
• Add support for Bedrock Edition?
• Add a thread pool and async requests to check a text file for online MC servers. (in progress in the devel branch)
• Maybe adding CL11 as a submodule isn't clever. If it works now, why not update it?
• Take into account SRV records so that FINALLY hypixel.net and any other domain (that have SRV records) actually work. (in progress in the devel branch)

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Why not Rust?

I objectively think Rust would be better for this project. But I also think C++ is awesome and deserves some love, it is also funny how easily I can shoot myself in the foot, thrilling.

📚 References & Acknowledgments

• Minecraft Protocol

• Server List Ping Protocol

• Packet Format

• String Format

• VarInt Logic

• ASIO library for socket programming

• CLI11 for CLI parsing