diff --git a/Cargo.lock b/Cargo.lock
index 111b81b..379e5d8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,185 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "anstream"
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+checksum = "824a212faf96e9acacdbd09febd34438f8f711fb84e09a8916013cd7815ca28d"
+dependencies = [
+ "anstyle",
+ "anstyle-parse",
+ "anstyle-query",
+ "anstyle-wincon",
+ "colorchoice",
+ "is_terminal_polyfill",
+ "utf8parse",
+]
+
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+ "utf8parse",
+]
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+]
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+dependencies = [
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+ "once_cell_polyfill",
+ "windows-sys",
+]
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+ "clap_derive",
+]
+
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+ "anstyle",
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+ "strsim",
+]
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+dependencies = [
+ "windows-link",
+]
diff --git a/Cargo.toml b/Cargo.toml
index 6e5a485..198c8d3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,3 +4,4 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+clap = { version = "4.6.4", features = ["derive"] }
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..924af4a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,131 @@
-fn main() {
-    println!("Hello, world!");
+use std::{io::{Read, Write}, net::{TcpStream, ToSocketAddrs}};
+use clap::Parser;
+
+#[derive(Parser, Debug)]
+struct Args {
+    #[arg(short, long)]
+    addr: String,
+
+    #[arg(short, long)]
+    password: String,
+
+    #[arg(short, long)]
+    cmd: String
 }
+
+#[derive(Clone, Copy, PartialEq)]
+enum PacketType {
+    Login = 3,
+    Command = 2,
+    Response = 0
+}
+
+impl PacketType {
+    fn to_le_bytes(&self) -> [u8; 4] {
+        (*self as i32).to_le_bytes()
+    }
+}
+
+impl TryFrom<i32> for PacketType {
+    type Error = ();
+
+    fn try_from(value: i32) -> Result<Self, Self::Error> {
+        match value {
+            x if x == Self::Login as i32 => Ok(Self::Login),
+            x if x == Self::Command as i32 => Ok(Self::Command),
+            x if x == Self::Response as i32 => Ok(Self::Response),
+            _ => Err(())
+        }
+    }
+}
+
+struct RconClient {
+    stream: TcpStream,
+    next_id: i32
+}
+
+impl RconClient {
+    fn read_i32_le(&mut self) -> i32 {
+        let mut buf = [0u8; 4];
+        self.stream.read_exact(&mut buf).unwrap();
+        i32::from_le_bytes(buf)
+    }
+
+    fn recv_packet(&mut self) -> (i32, PacketType, String) {
+        let length = self.read_i32_le();
+        if length < 10 {
+            panic!("response length < 10");
+        }
+
+        let id = self.read_i32_le();
+        let ptype = PacketType::try_from(self.read_i32_le()).unwrap();
+
+        let payload_len = (length - 10) as usize;
+        let mut payload_bytes = vec![0u8; payload_len];
+        self.stream.read_exact(&mut payload_bytes).unwrap();
+
+        let mut nulls = [0u8; 2];
+        self.stream.read_exact(&mut nulls).unwrap();
+
+        let payload = String::from_utf8_lossy(&payload_bytes).into_owned();
+        (id, ptype, payload)
+    }
+
+    fn send_packet(&mut self, ptype: PacketType, payload: &str) -> i32 {
+        let id = self.next_id;
+        self.next_id = self.next_id.wrapping_add(1);
+
+        let payload_bytes = payload.as_bytes();
+        let length = (payload_bytes.len() + 10) as i32;
+
+        let mut packet = Vec::with_capacity(4 + length as usize);
+        packet.extend_from_slice(&length.to_le_bytes());
+        packet.extend_from_slice(&id.to_le_bytes());
+        packet.extend_from_slice(&ptype.to_le_bytes());
+        packet.extend_from_slice(&payload_bytes);
+        packet.push(0); // terminate payload
+        packet.push(0); // padding
+
+        self.stream.write_all(&packet).unwrap();
+        id
+    }
+
+    fn authenticate(&mut self, password: &str) {
+        self.send_packet(PacketType::Login, password);
+
+        let (auth_id, _, _) = self.recv_packet();
+
+        if auth_id == -1 {
+            panic!("auth failed");
+        }
+    }
+    
+    fn connect(addr: impl ToSocketAddrs, password: &str) -> Self {
+        let stream = TcpStream::connect(addr).unwrap();
+        let mut client = RconClient { stream, next_id: 1 };
+        client.authenticate(password);
+        client
+    }
+
+    fn command(&mut self, cmd: &str) -> String {
+        let id = self.send_packet(PacketType::Command, cmd);
+
+        let (resp_id, resp_type, payload) = self.recv_packet();
+        if resp_type != PacketType::Response {
+            panic!("invalid response")
+        }
+        if resp_id != id {
+            panic!("invalid response")
+        }
+
+        payload
+    }
+}
+
+fn main() {
+    let args = Args::parse();
+
+    let mut client = RconClient::connect(args.addr, args.password.as_str());
+    let resp = client.command(&args.cmd);
+    println!("{resp}");
+}
\ No newline at end of file