diff --git a/Cargo.lock b/Cargo.lock
index 8eeb29e..e7401f9 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -28,6 +28,15 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "addr2line"
+version = "0.24.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dfbe277e56a376000877090da837660b4427aad530e3028d44e0bffe4f89a1c1"
+dependencies = [
+ "gimli",
+]
+
 [[package]]
 name = "adler2"
 version = "2.0.0"
@@ -400,6 +409,21 @@ version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ace50bade8e6234aa140d9a2f552bbee1db4d353f69b8217bc503490fc1a9f26"
 
+[[package]]
+name = "backtrace"
+version = "0.3.74"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8d82cb332cdfaed17ae235a638438ac4d4839913cc2af585c3c6746e8f8bee1a"
+dependencies = [
+ "addr2line",
+ "cfg-if",
+ "libc",
+ "miniz_oxide",
+ "object",
+ "rustc-demangle",
+ "windows-targets 0.52.6",
+]
+
 [[package]]
 name = "bindgen"
 version = "0.70.1"
@@ -1306,6 +1330,12 @@ dependencies = [
  "windows 0.58.0",
 ]
 
+[[package]]
+name = "gimli"
+version = "0.31.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "07e28edb80900c19c28f1072f2e8aeca7fa06b23cd4169cefe1af5aa3260783f"
+
 [[package]]
 name = "gl_generator"
 version = "0.14.0"
@@ -1736,6 +1766,7 @@ dependencies = [
  "serde",
  "serde_json",
  "thread-priority",
+ "tokio",
  "wgpu",
  "windows 0.58.0",
  "winit",
@@ -1902,6 +1933,17 @@ dependencies = [
  "simd-adler32",
 ]
 
+[[package]]
+name = "mio"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2886843bf800fba2e3377cff24abf6379b4c4d5c6681eaf9ea5b0d15090450bd"
+dependencies = [
+ "libc",
+ "wasi",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "naga"
 version = "23.1.0"
@@ -2276,6 +2318,15 @@ dependencies = [
  "objc2-foundation",
 ]
 
+[[package]]
+name = "object"
+version = "0.36.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62948e14d923ea95ea2c7c86c71013138b66525b86bdc08d2dcc262bdb497b87"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "oboe"
 version = "0.6.1"
@@ -2696,6 +2747,12 @@ dependencies = [
  "realfft",
 ]
 
+[[package]]
+name = "rustc-demangle"
+version = "0.1.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "719b953e2095829ee67db738b3bfa9fa368c94900df327b3f07fe6e794d2fe1f"
+
 [[package]]
 name = "rustc-hash"
 version = "1.1.0"
@@ -2918,6 +2975,16 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "socket2"
+version = "0.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c970269d99b64e60ec3bd6ad27270092a5394c4e309314b18ae3fe575695fbe8"
+dependencies = [
+ "libc",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "spirv"
 version = "0.3.0+sdk-1.3.268.0"
@@ -3070,6 +3137,33 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "tokio"
+version = "1.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5cec9b21b0450273377fc97bd4c33a8acffc8c996c987a7c5b319a0083707551"
+dependencies = [
+ "backtrace",
+ "bytes",
+ "libc",
+ "mio",
+ "pin-project-lite",
+ "socket2",
+ "tokio-macros",
+ "windows-sys 0.52.0",
+]
+
+[[package]]
+name = "tokio-macros"
+version = "2.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "693d596312e88961bc67d7f1f97af8a70227d9f90c31bba5806eec004978d752"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "toml"
 version = "0.8.19"
diff --git a/Cargo.toml b/Cargo.toml
index 54757fc..e5ea2be 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,6 +32,7 @@ rubato = "0.16"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 thread-priority = "1"
+tokio = { version = "1", features = ["io-util", "macros", "net", "rt", "sync"] }
 wgpu = "23"
 winit = { version = "0.30", features = ["serde"] }
 
diff --git a/src/app.rs b/src/app.rs
index 8c83a07..ec9fddc 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -18,7 +18,7 @@ use crate::{
     emulator::{EmulatorClient, EmulatorCommand, SimId},
     input::MappingProvider,
     persistence::Persistence,
-    window::{AboutWindow, AppWindow, GameWindow, InputWindow},
+    window::{AboutWindow, AppWindow, GameWindow, GdbServerWindow, InputWindow},
 };
 
 fn load_icon() -> anyhow::Result<IconData> {
@@ -183,6 +183,10 @@ impl ApplicationHandler<UserEvent> for Application {
                 let about = AboutWindow;
                 self.open(event_loop, Box::new(about));
             }
+            UserEvent::OpenDebugger(sim_id) => {
+                let debugger = GdbServerWindow::new(sim_id, self.client.clone());
+                self.open(event_loop, Box::new(debugger));
+            }
             UserEvent::OpenInput => {
                 let input = InputWindow::new(self.mappings.clone());
                 self.open(event_loop, Box::new(input));
@@ -374,6 +378,7 @@ impl Drop for Viewport {
 pub enum UserEvent {
     GamepadEvent(gilrs::Event),
     OpenAbout,
+    OpenDebugger(SimId),
     OpenInput,
     OpenPlayer2,
 }
diff --git a/src/emulator.rs b/src/emulator.rs
index 814149b..8748a10 100644
--- a/src/emulator.rs
+++ b/src/emulator.rs
@@ -1,5 +1,6 @@
 use std::{
     collections::HashMap,
+    fmt::Display,
     fs::{self, File},
     io::{Read, Seek, SeekFrom, Write},
     path::{Path, PathBuf},
@@ -45,6 +46,14 @@ impl SimId {
         }
     }
 }
+impl Display for SimId {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(match self {
+            Self::Player1 => "Player 1",
+            Self::Player2 => "Player 2",
+        })
+    }
+}
 
 struct Cart {
     rom_path: PathBuf,
diff --git a/src/gdbserver.rs b/src/gdbserver.rs
new file mode 100644
index 0000000..e763d1a
--- /dev/null
+++ b/src/gdbserver.rs
@@ -0,0 +1,154 @@
+use std::{
+    error::Error,
+    sync::{Arc, Mutex},
+    thread,
+};
+use tokio::{
+    io::{AsyncReadExt, AsyncWriteExt as _, BufReader, BufWriter},
+    net::{
+        tcp::{OwnedReadHalf, OwnedWriteHalf},
+        TcpListener, TcpStream,
+    },
+    select,
+    sync::oneshot,
+};
+
+use crate::emulator::{EmulatorClient, EmulatorCommand, SimId};
+
+pub struct GdbServer {
+    sim_id: SimId,
+    client: EmulatorClient,
+    status: Arc<Mutex<GdbServerStatus>>,
+    killer: Option<oneshot::Sender<()>>,
+}
+
+impl GdbServer {
+    pub fn new(sim_id: SimId, client: EmulatorClient) -> Self {
+        Self {
+            sim_id,
+            client,
+            status: Arc::new(Mutex::new(GdbServerStatus::Stopped)),
+            killer: None,
+        }
+    }
+
+    pub fn status(&self) -> GdbServerStatus {
+        self.status.lock().unwrap().clone()
+    }
+
+    pub fn start(&mut self, port: u16) {
+        let sim_id = self.sim_id;
+        let client = self.client.clone();
+        let status = self.status.clone();
+        let (tx, rx) = oneshot::channel();
+        self.killer = Some(tx);
+        thread::spawn(move || {
+            tokio::runtime::Builder::new_current_thread()
+                .enable_all()
+                .build()
+                .unwrap()
+                .block_on(async move {
+                    select! {
+                        _ = run_server(sim_id, client, port, &status) => {}
+                        _ = rx => {
+                            *status.lock().unwrap() = GdbServerStatus::Stopped;
+                        }
+                    }
+                })
+        });
+    }
+
+    pub fn stop(&mut self) {
+        if let Some(killer) = self.killer.take() {
+            let _ = killer.send(());
+        }
+    }
+}
+
+async fn run_server(
+    sim_id: SimId,
+    client: EmulatorClient,
+    port: u16,
+    status: &Mutex<GdbServerStatus>,
+) {
+    client.send_command(EmulatorCommand::Pause);
+    let Some(stream) = try_connect(port, status).await else {
+        return;
+    };
+    let connection = GdbConnection::new(sim_id, client, stream);
+    match connection.run().await {
+        Ok(()) => {
+            *status.lock().unwrap() = GdbServerStatus::Stopped;
+        }
+        Err(error) => {
+            *status.lock().unwrap() = GdbServerStatus::Error(error.to_string());
+        }
+    }
+}
+
+async fn try_connect(port: u16, status: &Mutex<GdbServerStatus>) -> Option<TcpStream> {
+    *status.lock().unwrap() = GdbServerStatus::Connecting;
+    let listener = match TcpListener::bind(("127.0.0.1", port)).await {
+        Ok(l) => l,
+        Err(err) => {
+            *status.lock().unwrap() = GdbServerStatus::Error(err.to_string());
+            return None;
+        }
+    };
+    match listener.accept().await {
+        Ok((stream, _)) => {
+            *status.lock().unwrap() = GdbServerStatus::Running;
+            Some(stream)
+        }
+        Err(err) => {
+            *status.lock().unwrap() = GdbServerStatus::Error(err.to_string());
+            None
+        }
+    }
+}
+
+#[derive(Clone)]
+pub enum GdbServerStatus {
+    Stopped,
+    Connecting,
+    Running,
+    Error(String),
+}
+
+impl GdbServerStatus {
+    pub fn running(&self) -> bool {
+        matches!(self, Self::Connecting | Self::Running)
+    }
+}
+
+struct GdbConnection {
+    sim_id: SimId,
+    client: EmulatorClient,
+    stream_in: BufReader<OwnedReadHalf>,
+    stream_out: BufWriter<OwnedWriteHalf>,
+}
+
+impl GdbConnection {
+    fn new(sim_id: SimId, client: EmulatorClient, stream: TcpStream) -> Self {
+        let (rx, tx) = stream.into_split();
+        Self {
+            sim_id,
+            client,
+            stream_in: BufReader::new(rx),
+            stream_out: BufWriter::new(tx),
+        }
+    }
+    async fn run(mut self) -> Result<(), Box<dyn Error>> {
+        println!("Connected for {}", self.sim_id);
+        self.client.send_command(EmulatorCommand::Resume);
+        loop {
+            let byte = self.read_byte().await?;
+            println!("{byte}");
+            self.stream_out.write_u8(byte).await?;
+        }
+    }
+
+    async fn read_byte(&mut self) -> std::io::Result<u8> {
+        self.stream_in.read_u8().await
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 642f9c5..e9abf8e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -14,6 +14,7 @@ mod app;
 mod audio;
 mod controller;
 mod emulator;
+mod gdbserver;
 mod graphics;
 mod input;
 mod persistence;
diff --git a/src/window.rs b/src/window.rs
index fd53acc..b60e9c3 100644
--- a/src/window.rs
+++ b/src/window.rs
@@ -1,12 +1,14 @@
 pub use about::AboutWindow;
 use egui::{Context, ViewportBuilder, ViewportId};
 pub use game::GameWindow;
+pub use gdb::GdbServerWindow;
 pub use input::InputWindow;
 use winit::event::KeyEvent;
 
 mod about;
 mod game;
 mod game_screen;
+mod gdb;
 mod input;
 
 pub trait AppWindow {
diff --git a/src/window/game.rs b/src/window/game.rs
index 2570d07..ced5d1d 100644
--- a/src/window/game.rs
+++ b/src/window/game.rs
@@ -121,6 +121,14 @@ impl GameWindow {
                 }
             }
         });
+        ui.menu_button("Tools", |ui| {
+            if ui.button("GDB Server").clicked() {
+                self.proxy
+                    .send_event(UserEvent::OpenDebugger(self.sim_id))
+                    .unwrap();
+                ui.close_menu();
+            }
+        });
         ui.menu_button("About", |ui| {
             self.proxy.send_event(UserEvent::OpenAbout).unwrap();
             ui.close_menu();
diff --git a/src/window/gdb.rs b/src/window/gdb.rs
new file mode 100644
index 0000000..c96c169
--- /dev/null
+++ b/src/window/gdb.rs
@@ -0,0 +1,80 @@
+use egui::{Button, CentralPanel, TextEdit, ViewportBuilder, ViewportId};
+
+use crate::{
+    emulator::{EmulatorClient, SimId},
+    gdbserver::{GdbServer, GdbServerStatus},
+};
+
+use super::AppWindow;
+
+pub struct GdbServerWindow {
+    sim_id: SimId,
+    port_str: String,
+    server: GdbServer,
+}
+
+impl GdbServerWindow {
+    pub fn new(sim_id: SimId, client: EmulatorClient) -> Self {
+        Self {
+            sim_id,
+            port_str: (8080 + sim_id.to_index()).to_string(),
+            server: GdbServer::new(sim_id, client),
+        }
+    }
+}
+
+impl AppWindow for GdbServerWindow {
+    fn viewport_id(&self) -> ViewportId {
+        ViewportId::from_hash_of(format!("Debugger-{}", self.sim_id))
+    }
+
+    fn initial_viewport(&self) -> ViewportBuilder {
+        ViewportBuilder::default()
+            .with_title(format!("GDB Server ({})", self.sim_id))
+            .with_inner_size((300.0, 200.0))
+    }
+
+    fn show(&mut self, ctx: &egui::Context) {
+        let port_num: Option<u16> = self.port_str.parse().ok();
+        let status = self.server.status();
+        CentralPanel::default().show(ctx, |ui| {
+            ui.horizontal(|ui| {
+                if port_num.is_none() {
+                    let style = ui.style_mut();
+                    let error = style.visuals.error_fg_color;
+                    style.visuals.widgets.active.bg_stroke.color = error;
+                    style.visuals.widgets.hovered.bg_stroke.color = error;
+                }
+                ui.label("Port");
+                let port_editor = TextEdit::singleline(&mut self.port_str).desired_width(100.0);
+                ui.add_enabled(!status.running(), port_editor);
+            });
+
+            if !status.running() {
+                let start_button = Button::new("Start");
+                if ui.add_enabled(port_num.is_some(), start_button).clicked() {
+                    let port = port_num.unwrap();
+                    self.server.start(port);
+                }
+            } else {
+                let stop_button = Button::new("Stop");
+                if ui.add(stop_button).clicked() {
+                    self.server.stop();
+                }
+            }
+
+            match &status {
+                GdbServerStatus::Stopped => {}
+                GdbServerStatus::Connecting => {
+                    ui.label("Connecting...");
+                }
+                GdbServerStatus::Running => {
+                    ui.label("Running");
+                }
+                GdbServerStatus::Error(message) => {
+                    ui.label(message);
+                }
+            }
+        });
+    }
+}