Add DASP device discovery to the connect dialog

Send DISCOVER broadcast (type 0) to 255.255.255.255 and the Sedona
multicast address 239.255.18.76 to find devices on the network.
Responses are listed in a Treeview showing IP and platform ID.
Selecting a device fills the Host field; double-click connects.
Wait time is configurable (default 10s, range 1-60s).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

connect_dialog.py

@@ -1,8 +1,10 @@
 """
 Connection dialog for connecting to a live Sedona device.
 
-Modal Toplevel with host, port, username, password fields.
-Connect runs in a background thread; progress and errors shown inline.
+Modal Toplevel with host, port, username, password fields and device
+discovery.  Connect runs in a background thread; progress and errors
+shown inline.  The Discover button sends a DASP broadcast and lists
+responding devices so the user can pick one.
 """
 
 import configparser
@@ -20,6 +22,7 @@ class ConnectDialog:
         self._callback = on_connect_callback
         self._thread = None
         self._cancelled = False
+        self._discover_thread = None
 
         self._dlg = tk.Toplevel(parent)
         self._dlg.title("Connect to Device")
@@ -56,6 +59,49 @@ class ConnectDialog:
         ttk.Entry(frame, textvariable=self._pass_var, width=28, show="*").grid(
             row=row, column=1, columnspan=2, sticky="ew", pady=4)
 
+        # ── Discovery section ──────────────────────────────────────
+        row += 1
+        sep = ttk.Separator(frame, orient="horizontal")
+        sep.grid(row=row, column=0, columnspan=3, sticky="ew", pady=(12, 4))
+
+        row += 1
+        disc_header = ttk.Frame(frame)
+        disc_header.grid(row=row, column=0, columnspan=3, sticky="ew", pady=(0, 4))
+
+        ttk.Label(disc_header, text="Discovered Devices:").pack(side=tk.LEFT)
+
+        self._btn_discover = ttk.Button(
+            disc_header, text="Discover", command=self._do_discover, width=10)
+        self._btn_discover.pack(side=tk.RIGHT)
+
+        self._wait_var = tk.StringVar(value="10")
+        wait_entry = ttk.Entry(disc_header, textvariable=self._wait_var, width=4,
+                               justify="center")
+        wait_entry.pack(side=tk.RIGHT, padx=(0, 4))
+        ttk.Label(disc_header, text="Wait (s):").pack(side=tk.RIGHT, padx=(8, 2))
+
+        row += 1
+        list_frame = ttk.Frame(frame)
+        list_frame.grid(row=row, column=0, columnspan=3, sticky="nsew", pady=(0, 4))
+        frame.rowconfigure(row, weight=1)
+
+        columns = ("ip", "platform")
+        self._dev_tree = ttk.Treeview(
+            list_frame, columns=columns, show="headings", height=5, selectmode="browse")
+        self._dev_tree.heading("ip", text="IP Address")
+        self._dev_tree.heading("platform", text="Platform ID")
+        self._dev_tree.column("ip", width=140, minwidth=100)
+        self._dev_tree.column("platform", width=180, minwidth=100)
+        self._dev_tree.pack(side=tk.LEFT, fill=tk.BOTH, expand=True)
+
+        scrollbar = ttk.Scrollbar(list_frame, orient="vertical", command=self._dev_tree.yview)
+        scrollbar.pack(side=tk.RIGHT, fill=tk.Y)
+        self._dev_tree.configure(yscrollcommand=scrollbar.set)
+
+        self._dev_tree.bind("<<TreeviewSelect>>", self._on_device_selected)
+        self._dev_tree.bind("<Double-1>", lambda e: self._do_connect())
+
+        # ── Status and buttons ─────────────────────────────────────
         row += 1
         self._status_label = ttk.Label(frame, text="", foreground="#666666")
         self._status_label.grid(row=row, column=0, columnspan=3, sticky="w", pady=(8, 4))
@@ -79,6 +125,77 @@ class ConnectDialog:
         y = parent.winfo_y() + (parent.winfo_height() - self._dlg.winfo_height()) // 2
         self._dlg.geometry(f"+{x}+{y}")
 
+    # ── Discovery ──────────────────────────────────────────────────
+
+    def _do_discover(self):
+        try:
+            port_int = int(self._port_var.get().strip())
+        except ValueError:
+            port_int = 1876
+
+        try:
+            wait_time = max(1, min(60, int(self._wait_var.get().strip())))
+        except ValueError:
+            wait_time = 10
+
+        self._btn_discover.config(state="disabled")
+        self._status_label.config(text="Discovering devices...", foreground="#666666")
+
+        for item in self._dev_tree.get_children():
+            self._dev_tree.delete(item)
+
+        self._discover_thread = threading.Thread(
+            target=self._discover_worker, args=(port_int, wait_time), daemon=True)
+        self._discover_thread.start()
+        self._poll_discover()
+
+    def _discover_worker(self, port, wait_time):
+        from dasp import DaspSocket
+        sock = None
+        try:
+            sock = DaspSocket()
+            devices = sock.discover(port=port, wait_time=wait_time)
+            self._discover_result = ("ok", devices)
+        except Exception as e:
+            self._discover_result = ("error", str(e))
+        finally:
+            if sock is not None:
+                try:
+                    sock.close()
+                except Exception:
+                    pass
+
+    def _poll_discover(self):
+        if self._discover_thread is not None and self._discover_thread.is_alive():
+            self._dlg.after(100, self._poll_discover)
+            return
+
+        status, data = self._discover_result
+        self._btn_discover.config(state="normal")
+
+        if status == "ok":
+            if data:
+                for ip, platform_id in data:
+                    self._dev_tree.insert("", tk.END, values=(ip, platform_id))
+                self._status_label.config(
+                    text=f"Found {len(data)} device(s)", foreground="#006600")
+            else:
+                self._status_label.config(
+                    text="No devices found", foreground="#666666")
+        else:
+            self._status_label.config(
+                text=f"Discovery error: {data}", foreground="#c00000")
+
+    def _on_device_selected(self, event):
+        sel = self._dev_tree.selection()
+        if not sel:
+            return
+        values = self._dev_tree.item(sel[0], "values")
+        if values:
+            self._host_var.set(values[0])
+
+    # ── Connect ────────────────────────────────────────────────────
+
     def _do_connect(self):
         host = self._host_var.get().strip()
         port = self._port_var.get().strip()
@@ -96,6 +213,7 @@ class ConnectDialog:
             return
 
         self._btn_connect.config(state="disabled")
+        self._btn_discover.config(state="disabled")
         self._status_label.config(text="Connecting...", foreground="#666666")
 
         self._cancelled = False
@@ -134,11 +252,11 @@ class ConnectDialog:
             msg = rest[0]
             self._status_label.config(text=f"Error: {msg}", foreground="#c00000")
             self._btn_connect.config(state="normal")
+            self._btn_discover.config(state="normal")
 
     def _do_cancel(self):
         self._cancelled = True
         if self._thread is not None and self._thread.is_alive():
-            # Connection attempt in progress — clean up after it finishes
             import app_state as _as
             def _cleanup():
                 self._thread.join(timeout=5)