Add project files.

Discovery/Discovery.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Inspectron.Epson\Inspectron.Epson.csproj" />
+  </ItemGroup>
+
+</Project>

Discovery/PrinterDiscoveryService.cs

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+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}"));
+    }
+}

Discovery/Program.cs

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+using Inspectron.Epson;
+
+Console.WriteLine("Listening for printer responses...\n");
+
+var discoveryService = new PrinterDiscoveryService();
+
+var printers = await discoveryService.DiscoverPrintersAsync(
+    timeout: TimeSpan.FromSeconds(5),
+    onPrinterDiscovered: printer =>
+    {
+        Console.WriteLine($"Received {printer.ResponseData.Length} bytes from {printer.IPAddress}");
+        Console.WriteLine(printer.GetResponseDataAsHex());
+        Console.WriteLine();
+    });
+
+Console.WriteLine($"\nDiscovery complete. Found {printers.Count} printer(s).");
+
+

Discovery/discovery.c

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+#include <stdio.h>
+#include <winsock.h>
+
+#define MAXBUF 512
+char buf[MAXBUF];
+
+int main(int argc, char* argv[])
+{
+    WSADATA data;
+    SOCKET sock;
+    struct sockaddr_in addr;
+    int i, len, fromlen;
+
+    if (argc != 2) {
+        printf("usage: wudp <IP address>\n");
+        exit(1);
+    }
+
+    /* initialize windows socket */
+    WSAStartup(0x0101, &data);
+
+    /* Create socket */
+    if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == INVALID_SOCKET) {
+        fprintf(stderr, "Error socket(): %d\n", WSAGetLastError());
+        exit(1);
+    }
+
+    /* initialize the parameter */
+    memset(&addr, 0, sizeof(addr));
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(3289);
+    addr.sin_addr.s_addr = inet_addr(argv[1]);
+
+    /* make a packet (PRINTER STATUS) */
+    buf[0] = 'E';
+    buf[1] = 'P';
+    buf[2] = 'S';
+    buf[3] = 'O';
+    buf[4] = 'N';
+    buf[5] = 'Q'; // PacketType(Q)
+    buf[6] = 0x03; // DeviceType(3)
+    buf[7] = 0x00; // DeviceNumber(0)
+    buf[8] = 0x00; // Function(0010h)
+    buf[9] = 0x10;
+    
+    buf[10] = 0x00; // Result
+    buf[11] = 0x00;
+    buf[12] = 0x00; // Parameter length
+    buf[13] = 0x00;
+
+    /* send a packet */
+    i = sendto(sock, buf, 14, 0, (struct sockaddr*)&addr, sizeof(addr));
+
+    /* receive packet */
+    fromlen = sizeof(addr);
+    len = recvfrom(sock, buf, MAXBUF, 0, (struct sockaddr*)&addr, &fromlen);
+
+    /* print receive packet */
+    if (len) {
+        if ((buf[10] == 0x00) && (buf[11] == 0x00))
+            for (i = 0; i < len; i++)
+                printf("%3d:%02Xh\n", i, buf[i] & 0xff);
+    }
+
+    /* close socket */
+    closesocket(sock);
+    return 0;
+}