Add live debugger frontend and mutex stall recovery (#383)

src/SharpEmu.DebugClient/ClientEndpoint.cs

@@ -0,0 +1,54 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System.Net;
+
+namespace SharpEmu.DebugClient;
+
+/// <summary>
+/// Parses the <c>host:port</c> the client connects to. Mirrors the server's
+/// defaults (loopback, port 5714) so a bare invocation attaches to a local
+/// emulator with no arguments.
+/// </summary>
+internal static class ClientEndpoint
+{
+    public const int DefaultPort = 5714;
+
+    public static bool TryParse(string? text, out string host, out int port, out string error)
+    {
+        host = "127.0.0.1";
+        port = DefaultPort;
+        error = string.Empty;
+        if (string.IsNullOrWhiteSpace(text))
+        {
+            return true;
+        }
+
+        var value = text.Trim();
+        var separator = value.LastIndexOf(':');
+        if (separator >= 0)
+        {
+            var portText = value[(separator + 1)..];
+            if (portText.Length > 0 && (!int.TryParse(portText, out port) || port is <= 0 or > 65535))
+            {
+                error = $"Invalid port '{portText}'.";
+                return false;
+            }
+
+            value = value[..separator];
+        }
+
+        if (!string.IsNullOrWhiteSpace(value))
+        {
+            host = string.Equals(value, "localhost", StringComparison.OrdinalIgnoreCase) ? "127.0.0.1" : value;
+        }
+
+        if (!IPAddress.TryParse(host, out _) && !Uri.CheckHostName(host).Equals(UriHostNameType.Dns))
+        {
+            error = $"Invalid host '{host}'.";
+            return false;
+        }
+
+        return true;
+    }
+}