lidgren-network-gen3/Lidgren.Network/NetConnection.Latency.cs

/* Copyright (c) 2010 Michael Lidgren

Permission is hereby granted, free of charge, to any person obtaining a copy of this software
and associated documentation files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom
the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
USE OR OTHER DEALINGS IN THE SOFTWARE.

*/
using System;
using System.Collections.Generic;
using System.Text;

namespace Lidgren.Network
{
	public partial class NetConnection
	{
		//
		// Connection keepalive and latency calculation
		//
		internal float m_averageRoundtripTime = 0.05f;
		private byte m_lastSentPingNumber;
		private double m_lastPingSendTime;
		private double m_nextPing;
		internal double m_lastSendRespondedTo;

		// remote + diff = local
		// diff = local - remote
		// local - diff = remote
		internal double m_remoteToLocalNetTime = double.MinValue;

		public float AverageRoundtripTime { get { return m_averageRoundtripTime; } }

		internal void InitializeLatency(float rtt, float remoteNetTime)
		{
			m_averageRoundtripTime = Math.Max(0.005f, rtt - 0.005f); // TODO: find out why initial ping always overshoots
			m_nextPing = NetTime.Now + m_peerConfiguration.m_pingFrequency / 2.0f;

			double currentRemoteNetTime = remoteNetTime - (rtt * 0.5);
			m_remoteToLocalNetTime = (float)(NetTime.Now - currentRemoteNetTime);

			StringBuilder bdr = new StringBuilder();
			bdr.Append("Initialized average roundtrip time to: ");
			bdr.Append(NetTime.ToReadable(m_averageRoundtripTime));
			bdr.Append(" remote time diff to ");
			bdr.Append(NetTime.ToReadable(m_remoteToLocalNetTime));
			m_owner.LogDebug(bdr.ToString());
		}

		internal void HandleIncomingPing(byte pingNumber)
		{
			double now = NetTime.Now;

			// send pong
			NetOutgoingMessage pong = m_owner.CreateMessage(1 + 8);
			pong.m_libType = NetMessageLibraryType.Pong;
			pong.Write((byte)pingNumber);
			pong.Write(now);

			m_owner.SendLibraryImmediately(pong, m_remoteEndpoint);
		}

		internal void HandleIncomingPong(double receiveNow, byte pingNumber, double remoteNetTime)
		{
			// verify it´s the correct ping number
			if (pingNumber != m_lastSentPingNumber)
			{
				m_owner.LogError("Received wrong pong number; got " + pingNumber + " expected " + m_lastSentPingNumber);

				// but still, a pong must have been triggered by a ping...
				double diff = receiveNow - m_lastSendRespondedTo;
				if (diff > 0)
					m_lastSendRespondedTo += (diff / 2); // postpone timing out a bit

				return;
			}
			
			double now = NetTime.Now; // need exact number

			m_lastHeardFrom = now;
			m_lastSendRespondedTo = m_lastPingSendTime;

			double rtt = now - m_lastPingSendTime;

			// update clock sync
			double currentRemoteNetTime = remoteNetTime - (rtt * 0.5);
			double foundDiffRemoteToLocal = receiveNow - currentRemoteNetTime;

			if (m_remoteToLocalNetTime == double.MinValue)
				m_remoteToLocalNetTime = foundDiffRemoteToLocal;
			else
				m_remoteToLocalNetTime = ((m_remoteToLocalNetTime + foundDiffRemoteToLocal) * 0.5);

			m_averageRoundtripTime = (m_averageRoundtripTime * 0.7f) + (float)(rtt * 0.3f);
			m_owner.LogVerbose("Found rtt: " + NetTime.ToReadable(rtt) + ", new average: " + NetTime.ToReadable(m_averageRoundtripTime) + " new time diff: " + NetTime.ToReadable(m_remoteToLocalNetTime));
		}

		internal void KeepAliveHeartbeat(double now)
		{
			// do keepalive and latency pings
			if (m_status == NetConnectionStatus.Disconnected || m_status == NetConnectionStatus.None)
				return;

			// force ack sending?
			if (now > m_nextForceAckTime)
			{
				// send keepalive thru regular channels to give acks something to piggyback on
				NetOutgoingMessage pig = m_owner.CreateMessage(1);
				pig.m_libType = NetMessageLibraryType.KeepAlive;
				SendLibrary(pig);
				m_nextForceAckTime = now + m_peerConfiguration.m_maxAckDelayTime;
			}

			// timeout
			if (now > m_lastSendRespondedTo + m_peerConfiguration.m_connectionTimeout)
			{
				Disconnect("Timed out after " + (now - m_lastSendRespondedTo) + " seconds");
				return;
			}

			// ping time?
			if (now >= m_nextPing)
			{
				//
				// send ping
				//
				now = NetTime.Now; // need exact number
				m_lastSentPingNumber++;
				m_lastPingSendTime = now;

				// in case of not heard for a while
				if (now > m_lastSendRespondedTo + (m_owner.Configuration.m_pingFrequency * 1.5f))
					m_nextPing = now + (m_owner.Configuration.m_pingFrequency * 0.5f); // double ping rate
				else
					m_nextPing = now + m_owner.Configuration.m_pingFrequency;

				NetOutgoingMessage ping = m_owner.CreateMessage(1);
				ping.m_libType = NetMessageLibraryType.Ping;
				ping.Write((byte)m_lastSentPingNumber);

				m_owner.SendLibraryImmediately(ping, m_remoteEndpoint);

			}
		}
	}
}