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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,109 @@ | ||
| using System; | ||
| using System.Collections.Generic; | ||
| using System.Diagnostics; | ||
| using System.Linq; | ||
| using System.Net; | ||
| using System.Net.Sockets; | ||
| using System.Text; | ||
|
|
||
| namespace plugin_Relay.Beacon; | ||
|
|
||
| public class Beacon : IDisposable | ||
| { | ||
| internal const int DiscoveryPort = 35891; | ||
| private readonly UdpClient _udp; | ||
|
|
||
| public Beacon(string beaconType, ushort advertisedPort) | ||
| { | ||
| BeaconType = beaconType; | ||
| AdvertisedPort = advertisedPort; | ||
| BeaconData = ""; | ||
|
|
||
| _udp = new UdpClient(); | ||
| _udp.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true); | ||
| _udp.Client.Bind(new IPEndPoint(IPAddress.Any, DiscoveryPort)); | ||
|
|
||
| try | ||
| { | ||
| _udp.AllowNatTraversal(true); | ||
| } | ||
| catch (Exception ex) | ||
| { | ||
| Debug.WriteLine("Error switching on NAT traversal: " + ex.Message); | ||
| } | ||
| } | ||
|
|
||
| public string BeaconType { get; } | ||
| public ushort AdvertisedPort { get; } | ||
| public bool Stopped { get; private set; } | ||
|
|
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| public string BeaconData { get; set; } | ||
|
|
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| public void Dispose() | ||
| { | ||
| Stop(); | ||
| } | ||
|
|
||
| public void Start() | ||
| { | ||
| Stopped = false; | ||
| _udp.BeginReceive(ProbeReceived, null); | ||
| } | ||
|
|
||
| public void Stop() | ||
| { | ||
| Stopped = true; | ||
| } | ||
|
|
||
| private void ProbeReceived(IAsyncResult ar) | ||
| { | ||
| var remote = new IPEndPoint(IPAddress.Any, 0); | ||
| var bytes = _udp.EndReceive(ar, ref remote); | ||
|
|
||
| // Compare beacon type to probe type | ||
| var typeBytes = Encode(BeaconType); | ||
| if (HasPrefix(bytes, typeBytes)) | ||
| { | ||
| // If true, respond again with our type, port and payload | ||
| var responseData = Encode(BeaconType) | ||
| .Concat(BitConverter.GetBytes((ushort)IPAddress.HostToNetworkOrder((short)AdvertisedPort))) | ||
| .Concat(Encode(BeaconData)).ToArray(); | ||
| _udp.Send(responseData, responseData.Length, remote); | ||
| } | ||
|
|
||
| if (!Stopped) _udp.BeginReceive(ProbeReceived, null); | ||
| } | ||
|
|
||
| internal static bool HasPrefix<T>(IEnumerable<T> haystack, IEnumerable<T> prefix) | ||
| { | ||
| var enumerable = haystack.ToList(); | ||
| var second = prefix.ToList(); | ||
|
|
||
| return enumerable.Count >= second.Count && | ||
| enumerable.Zip(second, (a, b) => a.Equals(b)).All(x => x); | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// Convert a string to network bytes | ||
| /// </summary> | ||
| internal static IEnumerable<byte> Encode(string data) | ||
| { | ||
| var bytes = Encoding.UTF8.GetBytes(data); | ||
| var len = IPAddress.HostToNetworkOrder((short)bytes.Length); | ||
|
|
||
| return BitConverter.GetBytes(len).Concat(bytes); | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// Convert network bytes to a string | ||
| /// </summary> | ||
| internal static string Decode(IEnumerable<byte> data) | ||
| { | ||
| var listData = data as IList<byte> ?? data.ToList(); | ||
|
|
||
| var len = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(listData.Take(2).ToArray(), 0)); | ||
| if (listData.Count < 2 + len) throw new ArgumentException("Too few bytes in packet"); | ||
|
|
||
| return Encoding.UTF8.GetString(listData.Skip(2).Take(len).ToArray()); | ||
| } | ||
| } |
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