Add project files.

Discovery/PrinterDiscoveryService.cs

@@ -0,0 +1,107 @@
+using System.Net;
+using System.Net.Sockets;
+
+namespace Inspectron.Epson;
+
+public class PrinterDiscoveryService
+{
+    private const int DiscoveryPort = 3289;
+    private const string DiscoveryMessage = "EPSONQ";
+    private const int MessageLength = 14;
+
+    /// <summary>
+    /// Discovers Epson printers on the local network using UDP broadcast
+    /// </summary>
+    /// <param name="timeout">How long to wait for responses (default: 5 seconds)</param>
+    /// <param name="onPrinterDiscovered">Optional callback invoked when a printer is discovered</param>
+    /// <returns>List of discovered printer information</returns>
+    public async Task<List<DiscoveredPrinter>> DiscoverPrintersAsync(
+        TimeSpan? timeout = null,
+        Action<DiscoveredPrinter>? onPrinterDiscovered = null)
+    {
+        timeout ??= TimeSpan.FromSeconds(5);
+
+        using var udpClient = new UdpClient();
+        udpClient.Client.Bind(new IPEndPoint(IPAddress.Any, 0));
+
+        // Send discovery broadcast message
+        var msg = BuildDiscoveryMessage();
+        var broadcastEndpoint = new IPEndPoint(IPAddress.Broadcast, DiscoveryPort);
+        await udpClient.SendAsync(msg, msg.Length, broadcastEndpoint);
+
+        // Receive responses
+        var discoveredPrinters = new List<DiscoveredPrinter>();
+        var endTime = DateTime.UtcNow.Add(timeout.Value);
+
+        while (DateTime.UtcNow < endTime)
+        {
+            try
+            {
+                var remainingTime = endTime - DateTime.UtcNow;
+                if (remainingTime <= TimeSpan.Zero)
+                    break;
+
+                var receiveTask = udpClient.ReceiveAsync();
+                var timeoutTask = Task.Delay(remainingTime);
+                var completedTask = await Task.WhenAny(receiveTask, timeoutTask);
+
+                if (completedTask == receiveTask)
+                {
+                    var result = await receiveTask;
+
+                    // Check if we've already discovered this printer
+                    if (!discoveredPrinters.Any(p => p.IPAddress.Equals(result.RemoteEndPoint.Address)))
+                    {
+                        var printer = new DiscoveredPrinter
+                        {
+                            IPAddress = result.RemoteEndPoint.Address,
+                            ResponseData = result.Buffer,
+                            DiscoveredAt = DateTime.UtcNow
+                        };
+
+                        discoveredPrinters.Add(printer);
+                        onPrinterDiscovered?.Invoke(printer);
+                    }
+                }
+                else
+                {
+                    break; // Timeout reached
+                }
+            }
+            catch (Exception)
+            {
+                // Ignore errors and continue waiting for other responses
+                break;
+            }
+        }
+
+        return discoveredPrinters;
+    }
+
+    private static byte[] BuildDiscoveryMessage()
+    {
+        // msg = b'EPSONQ' + bytes([0x00] * 8)
+        var msg = new byte[MessageLength];
+        Array.Copy(System.Text.Encoding.ASCII.GetBytes(DiscoveryMessage), msg, 6);
+        msg[6] = 3;
+        for (int i = 7; i < msg.Length; i++)
+        {
+            msg[i] = 0x00;
+        }
+
+        msg[10] = 0x10;
+        return msg;
+    }
+}
+
+public class DiscoveredPrinter
+{
+    public required IPAddress IPAddress { get; init; }
+    public required byte[] ResponseData { get; init; }
+    public DateTime DiscoveredAt { get; init; }
+
+    public string GetResponseDataAsHex()
+    {
+        return string.Join(" ", ResponseData.Select(b => $"{b:X2}"));
+    }
+}