diff --git a/app.py b/app.py
new file mode 100644
index 0000000..76efb1f
--- /dev/null
+++ b/app.py
@@ -0,0 +1,176 @@
+#!/usr/bin/env python3
+
+import tkinter as tk
+from tkinter import ttk, messagebox, simpledialog
+from typing import final
+from netbrite import (
+    NetBrite,
+    NetbriteConnectionException,
+    NetbriteTransferException,
+    Zone,
+    Message,
+)
+
+WIDTH = 300
+DEFAULT_ZONE = Zone(0, 0, 150, 7)
+DEFAULT_ZONE_NAME = "default"
+
+
+@final
+class SignControlGUI(tk.Tk):
+    def __init__(self):
+        super().__init__()
+        self.title("SignControl")
+        self.geometry(f"{WIDTH}x350")
+        self.resizable(False, True)
+
+        self.devices: list[NetBrite] = []
+
+        self._build_ui()
+
+    def _build_ui(self):
+        frm_devices = ttk.LabelFrame(self, text="Devices")
+        frm_devices.pack(fill="both", expand=True, padx=5, pady=5)
+
+        self.radios_frame = ttk.Frame(frm_devices)
+        self.radios_frame.pack(fill="both", expand=True, padx=5, pady=5)
+
+        self.selected_index = tk.IntVar(value=-1)
+
+        btn_frm = ttk.Frame(frm_devices)
+        btn_frm.pack(fill="both", padx=5, pady=5)
+        ttk.Button(btn_frm, text="Add", command=self._add_device).pack(side="left")
+        ttk.Button(btn_frm, text="Remove", command=self._remove_device).pack(
+            side="left"
+        )
+
+        frm_msg = ttk.LabelFrame(self, text="Message")
+        frm_msg.pack(fill="both", expand=False, padx=5, pady=5)
+        self.txt = tk.Text(frm_msg, height=1, wrap="word")
+        self.txt.pack(fill="both", expand=False, padx=5, pady=5)
+
+        hint = (
+            "Templates: {scrollon} {scrolloff} {blinkon} {blinkoff} "
+            "{left} {center} {right} {erase} {serialnum} {bell} "
+            "{red} {green} {yellow} {font <name>}"
+            "\nFonts: normal_7 normal_5 bold_7 monospace"
+        )
+        ttk.Label(
+            self,
+            text=hint,
+            font=("Segoe UI", 8),
+            foreground="gray",
+            wraplength=WIDTH - 20,
+            justify="center",
+        ).pack(
+            padx=5,
+            pady=(0, 5),
+        )
+
+        btm_btn_frm = ttk.Frame(self)
+        btm_btn_frm.pack(fill="y", padx=5, pady=5)
+        ttk.Button(btm_btn_frm, text="Send", command=self._send_message).pack(
+            side="left"
+        )
+        ttk.Button(btm_btn_frm, text="Reset", command=self._reset_selected_zone).pack(
+            side="left"
+        )
+        ttk.Button(btm_btn_frm, text="Quit", command=self.quit).pack(side="right")
+
+        _ = self.bind("<Return>", lambda e: self._send_message())
+
+    def _get_selection(self) -> tuple[int, NetBrite] | None:
+        idx = self.selected_index.get()
+        if idx == -1:
+            _ = messagebox.showwarning("No device", "Please select a device first.")
+            return None
+        return idx, self.devices[idx]
+
+    def _add_device(self):
+        ip = simpledialog.askstring("Add device", "IP address:")
+        if not ip:
+            return
+        self._add_device_ip(ip.strip())
+
+    def _add_device_ip(self, ip: str):
+        try:
+            device = NetBrite(ip)
+            length = len(self.devices)
+
+            self._reset_zone(device)
+            self.devices.append(device)
+
+            radio = ttk.Radiobutton(
+                self.radios_frame,
+                text=ip,
+                value=length,
+                variable=self.selected_index,
+            )
+            radio.pack(anchor="w")
+
+            self.selected_index.set(length)
+
+        except NetbriteConnectionException as exc:
+            _ = messagebox.showerror("Connection error", str(exc))
+
+    def _remove_device(self):
+        sel = self._get_selection()
+        if sel is None:
+            return
+        idx, _ = sel
+
+        _ = self.devices.pop(idx)
+
+        radio = self.radios_frame.winfo_children()[idx]
+        radio.destroy()
+
+        for new_idx, widget in enumerate(self.radios_frame.winfo_children()):
+            if isinstance(widget, ttk.Radiobutton):
+                _ = widget.configure(value=new_idx)
+
+        self.selected_index.set(
+            -1 if not self.devices else min(idx, len(self.devices) - 1)
+        )
+
+    def _send_message(self):
+        sel = self._get_selection()
+        if sel is None:
+            return
+
+        _, dev = sel
+        raw_text = self.txt.get("1.0", "end-1c").strip()
+        if not raw_text:
+            return
+
+        msg = Message("{erase}" + raw_text)
+        try:
+            dev.message(msg, DEFAULT_ZONE_NAME)
+            self.txt.delete("1.0", "end")
+        except NetbriteTransferException as exc:
+            _ = messagebox.showerror(
+                "Send failed, try removing and adding the device.", str(exc)
+            )
+
+    def _reset_selected_zone(self):
+        sel = self._get_selection()
+        if sel is None:
+            return
+
+        _, dev = sel
+        self._reset_zone(dev)
+
+    def _reset_zone(self, device: NetBrite):
+        zone = DEFAULT_ZONE
+        message = Message("hello")
+
+        try:
+            device.zones({DEFAULT_ZONE_NAME: zone})
+            device.message(message, DEFAULT_ZONE_NAME)
+        except NetbriteTransferException as exc:
+            _ = messagebox.showerror(
+                "Send failed, try removing and adding the device.", str(exc)
+            )
+
+
+if __name__ == "__main__":
+    SignControlGUI().mainloop()
diff --git a/flake.nix b/flake.nix
index 53bf9e0..5739b33 100644
--- a/flake.nix
+++ b/flake.nix
@@ -15,7 +15,7 @@
         nativeBuildInputs = [
           pkgs.entr
           pkgs.fastapi-cli
-          (pkgs.python3.withPackages (x: [x.crc x.fastapi]))
+          (pkgs.python3.withPackages (x: [x.crc x.fastapi x.sqlmodel x.sqlalchemy x.tkinter]))
         ];
       };
   };
diff --git a/netbrite.py b/netbrite.py
index ba97efb..1a39dbb 100644
--- a/netbrite.py
+++ b/netbrite.py
@@ -10,6 +10,14 @@ import re
 DEFAULT_PORT = 700
 
 
+class NetbriteConnectionException(Exception):
+    pass
+
+
+class NetbriteTransferException(Exception):
+    pass
+
+
 class Colors(Enum):
     RED = 0x01
     GREEN = 0x02
@@ -101,7 +109,7 @@ class Message:
             (rb"\{right\}", b"\x10\x28"),
             (rb"\{pause\}", b"\x10\x05"),
             (rb"\{erase\}", b"\x10\x03"),
-            (rb"\{serial\}", b"\x10\x09"),
+            (rb"\{serialnum\}", b"\x10\x09"),
             (rb"\{bell\}", b"\x10\x05"),
             (rb"\{red\}", b"\x10\x0c" + pack("B", Colors.RED.value)),
             (rb"\{green\}", b"\x10\x0c" + pack("B", Colors.GREEN.value)),
@@ -183,16 +191,26 @@ class NetBrite:
 
         try:
             self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-            self.sock.settimeout(5000)
+            self.sock.settimeout(2)
             self.connect()
         except OSError as e:
-            raise ConnectionError(f"Error while opening network socket. {e}")
+            raise NetbriteConnectionException(
+                f"Error while opening network socket. {e}"
+            )
 
     def connect(self):
-        self.sock.connect((self.address, self.port))
+        try:
+            self.sock.connect((self.address, self.port))
+        except OSError as e:
+            raise NetbriteConnectionException(
+                f"Error while opening network socket. {e}"
+            )
 
     def tx(self, pkt: bytes):
-        _ = self.sock.send(pkt)
+        try:
+            _ = self.sock.send(pkt)
+        except OSError as e:
+            raise NetbriteTransferException(f"Error while opening network socket. {e}")
 
     def message(self, msg: Message, zoneName: str):
         z = self.zones_list.get(zoneName)