/// <summary>
/// Event handler for polling timer. Look for new devices and remove old ones.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private static void FindDeviceTimer_Elapsed(object sender, ElapsedEventArgs e)
{
TimeSinceReCheck += QueryInterval;
if (TimeSinceReCheck - ReCheckInterval > 0)
{
TimeSinceReCheck = 0;
var enumerator = DeviceList.GetEnumerator();
while (enumerator.MoveNext())
{
var key = enumerator.Current.Key;
try
{
// If it is time to recheck devices, mark every device as not discovered
if (!DeviceList.TryUpdate(key, false, true))
{
// TryUpdate returned false.
// The device has already was not found the previous recheck cycle. Assume it is gone and notify the user.
bool ret;
if (DeviceList.TryRemove(key, out ret))
{
PrintQueue.Enqueue($"Lost: {key}");
}
}
}
catch (KeyNotFoundException) { } // Device was already removed.
}
}
// Look for new and previously discovered devices
MDns.SendQuery(ServiceToQuery);
}
/// <summary>
/// Called when a DNS reply is received.
/// </summary>
/// <param name="sender">The MulticastService that sent the query.</param>
/// <param name="e">The device that replied.</param>
private static void MDns_AnswerReceived(object sender, MessageEventArgs e)
{
// Extract the DNS-SD service that replied, and the device's IP addresses
// Replies might be in Answers or AdditionalRecords so check both
var srvRecords = e.Message.AdditionalRecords.Union(e.Message.Answers).OfType <SRVRecord>().Distinct();
var ipv4s = e.Message.AdditionalRecords.Union(e.Message.Answers).OfType <ARecord>().OrderBy(x => x.Address.ToString());
var ipv6s = e.Message.AdditionalRecords.Union(e.Message.Answers).OfType <AAAARecord>().OrderBy(x => x.Address.ToString());
// Ensure the service we found matches the service we are looking for.
if (srvRecords.Count() == 0 || !srvRecords.Any(x => x.CanonicalName.EndsWith(ServiceToQuery)))
{
return;
}
// Ensure the service supports the desired settings
if (DisplayIPv6 && (ipv6s.Count() == 0 || (ipv6s.All(x => !x.Address.IsIPv6LinkLocal) && LinkLocalOnly)))
{
return;
}
if (DisplayIPv4 && (ipv4s.Count() == 0 || (ipv4s.All(x => !x.Address.ToString().StartsWith("169.254", StringComparison.InvariantCultureIgnoreCase) && LinkLocalOnly))))
{
return;
}
// Build device information string
string output = "";
bool shouldAdd = true;
// Only show link-local IPs if requested
if (DisplayHostname)
{
var host = ipv4s.Select(x => x.CanonicalName).FirstOrDefault();
if (host != null)
{
output += host + " ";
}
else
{
shouldAdd = false;
}
}
if (DisplayIPv4)
{
if (ipv4s.Count() > 0)
{
foreach (var ip in ipv4s)
{
output += ip.Address + " ";
}
}
else
{
shouldAdd = false;
}
}
if (DisplayIPv6)
{
if (ipv6s.Count() > 0)
{
foreach (var ip in ipv6s)
{
if (ip.Address.IsIPv6LinkLocal || !LinkLocalOnly)
{
output += ip.Address + " ";
}
}
}
else
{
shouldAdd = false;
}
}
if (DisplayPort)
{
output += srvRecords.First().Port + " ";
}
if (shouldAdd)
{
if (DeviceList.TryAdd(output, true))
{
PrintQueue.Enqueue($"Discovered: {output}");
}
else // Device has been discovered already.
{
// Mark the device as discovered (again) to ensure it isn't removed by the recheck logic.
DeviceList.TryUpdate(output, true, false);
}
}
}