GameCult.Networking: RUDP socket transports drop and count strays
A malformed frame, a foreign connection id or a packet the session refuses threw out of TryReceiveOnce. They are now counted in Stats.PacketsDropped and the read reports progress. The client-side transport checks the connection id before it claims the peer endpoint; the server listener drops refused packets instead of throwing. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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2 changed files with 128 additions and 8 deletions
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@ -33,6 +33,12 @@ namespace GameCult.Networking
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/// Gets the number of bytes received, including transport framing.
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/// </summary>
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public long BytesReceived { get; internal set; }
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/// <summary>
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/// Gets the number of datagrams read and discarded because they belong to no session on
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/// this transport: malformed frames, another session's connection id, a sender that is not
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/// the peer, or a packet the session refuses.
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/// </summary>
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public long PacketsDropped { get; internal set; }
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internal CultNetTransportStats Snapshot()
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{
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@ -41,7 +47,8 @@ namespace GameCult.Networking
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FramesSent = FramesSent,
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FramesReceived = FramesReceived,
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BytesSent = BytesSent,
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BytesReceived = BytesReceived
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BytesReceived = BytesReceived,
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PacketsDropped = PacketsDropped
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};
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}
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}
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@ -2081,23 +2088,55 @@ namespace GameCult.Networking
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}
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_stats.BytesReceived += received;
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// What a datagram carries is the sender's business, not a fault of this process: a
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// malformed frame, another session's connection id, a sender that is not the peer and
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// a packet the session refuses are dropped and counted. Only the socket ends a loop.
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// The id is checked before the peer endpoint is claimed, so a stray cannot become it.
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var wire = new byte[received];
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Array.Copy(buffer, wire, received);
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CultNetRudpPacket packet;
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try
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{
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packet = CultNetRudpPacketCodec.Decode(wire);
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}
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catch (Exception error) when (error is InvalidOperationException || error is ArgumentException)
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{
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_stats.PacketsDropped++;
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return true;
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}
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if (packet.ConnectionId != _session.ConnectionId)
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{
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_stats.PacketsDropped++;
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return true;
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}
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if (_remoteEndPoint == null)
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{
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_remoteEndPoint = remote;
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}
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else if (!_remoteEndPoint.Equals(remote))
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{
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_stats.PacketsDropped++;
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return true;
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}
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var wire = new byte[received];
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Array.Copy(buffer, wire, received);
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var packet = CultNetRudpPacketCodec.Decode(wire);
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TracePacket("rx", packet, received, remote);
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if (_mode == CultNetRudpSocketMode.Server && packet.PacketType == CultNetRudpPacketType.Connect)
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{
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lock (_sessionGate)
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SendPacket(_session.AcceptConnect(packet, NowMs()));
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{
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CultNetRudpPacket accept;
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try
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{
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accept = _session.AcceptConnect(packet, NowMs());
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}
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catch (InvalidOperationException)
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{
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_stats.PacketsDropped++;
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return true;
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}
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SendPacket(accept);
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}
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return true;
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}
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@ -2105,7 +2144,15 @@ namespace GameCult.Networking
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CultNetRudpPacket? acknowledgement = null;
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lock (_sessionGate)
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{
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result = _session.Receive(packet, NowMs());
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try
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{
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result = _session.Receive(packet, NowMs());
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}
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catch (InvalidOperationException)
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{
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_stats.PacketsDropped++;
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return true;
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}
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if (result.Reply != null)
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SendPacket(result.Reply);
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SendPackets(result.ReadyToSend);
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@ -2478,13 +2525,15 @@ namespace GameCult.Networking
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{
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packet = CultNetRudpPacketCodec.Decode(wire);
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}
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catch (InvalidOperationException)
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catch (Exception error) when (error is InvalidOperationException || error is ArgumentException)
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{
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_stats.PacketsDropped++;
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return true;
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}
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if (packet.ConnectionId != _connectionId)
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{
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_stats.PacketsDropped++;
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return true;
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}
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@ -2508,6 +2557,7 @@ namespace GameCult.Networking
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if (!_peers.TryGetValue(peerKey, out var existingPeer))
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{
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_stats.PacketsDropped++;
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return true;
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}
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@ -2515,7 +2565,15 @@ namespace GameCult.Networking
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CultNetRudpPacket? acknowledgement = null;
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lock (existingPeer.SessionGate)
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{
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result = existingPeer.Session.Receive(packet, NowMs());
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try
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{
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result = existingPeer.Session.Receive(packet, NowMs());
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}
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catch (InvalidOperationException)
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{
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_stats.PacketsDropped++;
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return true;
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}
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if (result.Reply != null)
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SendPacket(existingPeer.RemoteEndPoint, result.Reply);
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SendPackets(existingPeer, result.ReadyToSend);
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@ -1193,6 +1193,68 @@ namespace GameCult.Networking.Tests
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}
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[Test]
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public void RudpSocketTransport_DropsStraysAndKeepsServingItsPeer()
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{
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using var serverSocket = BindUdpSocket();
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using var clientSocket = BindUdpSocket();
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using var strayHost = BindUdpSocket();
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var serverEndPoint = serverSocket.LocalEndPoint!;
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var clientEndPoint = clientSocket.LocalEndPoint!;
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const uint connectionId = 0x10203050;
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using var server = new CultNetRudpSocketTransportConnection(new CultNetRudpSocketTransportOptions
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{
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RuntimeId = "csharp-rudp-server",
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Socket = serverSocket,
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Mode = CultNetRudpSocketMode.Server,
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ConnectionId = connectionId
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});
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using var client = new CultNetRudpSocketTransportConnection(new CultNetRudpSocketTransportOptions
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{
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RuntimeId = "csharp-rudp-client",
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Socket = clientSocket,
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Mode = CultNetRudpSocketMode.Client,
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RemoteEndPoint = serverEndPoint,
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ConnectionId = connectionId
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});
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var foreign = new CultNetRudpSession(new CultNetRudpSessionOptions { ConnectionId = 0x0BADF10E });
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var strays = new[]
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{
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Encoding.UTF8.GetBytes("not a rudp packet"),
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new byte[] { 1 },
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CultNetRudpPacketCodec.Encode(foreign.CreateConnect(0, Encoding.UTF8.GetBytes("foreign")))
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};
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// A stray that arrives before the peer must not become the peer.
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foreach (var stray in strays)
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strayHost.SendTo(stray, serverEndPoint);
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for (var index = 0; index < strays.Length; index++)
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Assert.That(server.ReceiveOnce(), Is.Null);
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Assert.That(server.Stats.PacketsDropped, Is.EqualTo(strays.Length));
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client.Connect(Encoding.UTF8.GetBytes("join"));
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PumpRudpHandshake(client, server);
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// A moved flow answers from the peer's own address with someone else's session.
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foreach (var stray in strays)
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{
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serverSocket.SendTo(stray, clientEndPoint);
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clientSocket.SendTo(stray, serverEndPoint);
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}
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for (var index = 0; index < strays.Length; index++)
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{
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Assert.That(client.ReceiveOnce(), Is.Null);
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Assert.That(server.ReceiveOnce(), Is.Null);
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}
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Assert.That(client.Stats.PacketsDropped, Is.EqualTo(strays.Length));
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Assert.That(server.Stats.PacketsDropped, Is.EqualTo(2 * strays.Length));
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client.Send("schema", Encoding.UTF8.GetBytes("still here"));
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Assert.That(Encoding.UTF8.GetString(ReceiveRudpFrame(server).Payload), Is.EqualTo("still here"));
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server.Send("schema", Encoding.UTF8.GetBytes("server still here"));
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Assert.That(Encoding.UTF8.GetString(ReceiveRudpFrame(client).Payload), Is.EqualTo("server still here"));
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}
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[Test]
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public void RudpSocketTransport_CarriesCultNetSchemaMessages()
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{
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