yarcon

Yet Another RCON is a small console client for sending administration commands to game servers over RCON. The code is protocol-oriented rather than game-specific: yarcon currently speaks Source RCON over TCP and Battleye RCON over UDP, then passes the command text through to the server.

Protocol Support

Protocol	Transport	Typical servers
Source RCON	TCP	Source Dedicated Server games, Project Zomboid, 7 Days to Die, Rust Legacy, Minecraft Java servers that expose Source-style RCON
Battleye RCON	UDP	DayZ, Arma 2/3 and other Battleye-enabled servers

Game support depends on the server exposing a compatible RCON endpoint and accepting the command you send. yarcon does not maintain game-specific sessions or command parsers.

Installing

Build the binary with the bundled script:

./build.sh

The script compiles the CLI entry point in yarcon.c with gcc and writes the executable to ./yarcon.

Requirements:

• Linux or another POSIX-like system with sockets support
• gcc
• bash

Usage

./yarcon -H HOST -p PORT -P PASSWORD -c COMMAND [OPTIONS]

Required arguments:

• -H, --host HOST: server host name or IP address.
• -p, --port PORT: RCON port. It must be a number from 1 to 65535.
• -P, --password PASS: RCON password.
• -c, --command CMD: command to run on the server.

Options:

• -b, --battleye: use Battleye RCON over UDP. Without this flag, yarcon uses Source RCON over TCP.
• -f, --config FILE: read host and port from a config file. CLI values take precedence.
• -d, --debug: print connection settings and protocol-level packet traces before sending the command.
• -h, --help: print usage information.

Examples:

# Source RCON
./yarcon -H 127.0.0.1 -p 27015 -P password -c status

# Minecraft Java RCON
./yarcon -H 127.0.0.1 -p 25575 -P password -c list

# Battleye RCON
./yarcon -b -H 127.0.0.1 -p 2301 -P password -c players

Config files support host: value and port: value lines:

host: 127.0.0.1
port: 16261

Then run:

./yarcon -f server.conf -P password -c players

Debugging

Use -d when an RCON server connects but does not answer as expected:

./yarcon -d -H 127.0.0.1 -p 25575 -P password -c list
./yarcon -b -d -H 127.0.0.1 -p 2301 -P password -c players

Debug output goes to stderr and includes:

• TCP connection start and success.
• Source RCON packets sent and received with size, id, type, total length and body length.
• Auth response and auth confirmation packets. A failed password is shown as id=-1.
• Battleye UDP packets sent and received with packet size, payload size, checksum, packet type and body preview.
• Read failures as timeout, connection closed, socket error, or malformed packet.

The auth password body is redacted in debug output. Command and response bodies are shown as escaped previews.

Command Examples

RCON commands are owned by each game server, not by yarcon. Treat the table below as a starting point and check your server's current command reference before using destructive commands such as ban, kick, shutdown, restart, or save.

Server family	Protocol flag	Useful discovery commands	Common administration commands
Source Dedicated Server games	default Source RCON	status, cvarlist, help <command>	say <message>, kick <name or userid>, banid <minutes> <steamid>, changelevel <map>
Project Zomboid	default Source RCON	players, help	servermsg "message", save, quit, kickuser "username" -r "reason", banuser "username"
7 Days to Die	default Source RCON	help, listplayers, version	say "message", kick <entityid or steamid> <reason>, ban add <name or id> <duration> <reason>, saveworld, shutdown
Rust Legacy	default Source RCON	status, find .	say "message", kick "player", banid <steamid>, save.all
DayZ / Arma Battleye	-b, --battleye	commands, version, players, admins	say -1 <message>, kick <player #> <reason>, ban <player #> <minutes> <reason>, bans, removeBan <ban #>
Arma server commands through Battleye	-b, --battleye	missions, players	#missions, #mission <missionName>, #restart, #reassign, #shutdown
Minecraft Java RCON	default Source RCON-compatible framing	list, help	say <message>, kick <player> [reason], ban <player> [reason], save-all, stop

Some games require commands to be entered without the in-game slash when sent through RCON. For example, an in-game /save command may be sent as save.

For Minecraft Java, enable RCON in server.properties before connecting:

enable-rcon=true
rcon.password=password
rcon.port=25575

Minecraft Golden Age / Beta 1.7.3

Minecraft Beta 1.7.3, often treated as the "Golden Age" release, does not implement RCON. Minecraft Java RCON was introduced later, in Beta 1.9 Prerelease. Publishing or exposing port 25575 in Docker is not enough: the server.jar itself must open and speak RCON on that port.

For a Beta 1.7.3 server, this can look misleading:

docker-compose ps   # shows 25575:25575 published
ss on the host      # shows Docker listening on 0.0.0.0:25575
nc from a client    # returns "Connection refused"

In that case yarcon is not reaching an RCON server; Docker is publishing a port that the Minecraft process inside the container does not actually serve. Check from inside the container:

docker exec -it mc-beta173 sh
ss -ltnp
grep -i rcon /data/server.properties

If only 25565 is listening and there are no enable-rcon, rcon.password, or rcon.port properties, the server version has no native RCON support. Use a newer Minecraft Java server, a mod/wrapper/proxy that exposes remote console control, or manage the process through Docker/stdin/logs instead of RCON.

Implementation Notes

• yarcon.c is the production CLI entry point.
• yarcon.h contains packet helpers for Source and Battleye RCON.
• Source RCON reads now follow Minecraft-compatible packet framing: read the 4-byte size first, read the exact payload length, and reject failed auth responses.
• game_response.h contains optional, game-agnostic response parsing helpers for future command-specific features.
• Game-specific experiments and hardcoded probe code have been removed from the default project tree so the client stays protocol-focused.

The current CLI validates required arguments, checks port ranges, bounds packet payloads before serialization, avoids config parser leaks, and sends the whole TCP packet even when send(2) writes only part of the buffer.

References

• Source RCON Protocol
• Battleye RCON Protocol
• Project Zomboid dedicated server
• Project Zomboid administration commands
• 7 Days to Die serveradmin.xml command permissions
• Bohemia BattlEye RCON notes
• Minecraft server commands
• @n0la rcon
• @Tiiffi mcrcon
• rconc
• @MultiMote battleye-rcon implemented in C
• How to Code a Server and Client in C with Sockets on Linux – Code Examples
• Simple C example of doing an HTTP POST and consuming the response
• Battleye RCON c test