// Executed at the client when we receive a Pong message
// find out how long it took since we sent the Ping
// and update time offset
internal void OnClientPong(NetworkPongMessage msg)
{
double now = LocalTime();
// how long did this message take to come back
double newRtt = now - msg.clientTime;
_rtt.Add(newRtt);
// the difference in time between the client and the server
// but subtract half of the rtt to compensate for latency
// half of rtt is the best approximation we have
double newOffset = now - newRtt * 0.5f - msg.serverTime;
double newOffsetMin = now - newRtt - msg.serverTime;
double newOffsetMax = now - msg.serverTime;
offsetMin = Math.Max(offsetMin, newOffsetMin);
offsetMax = Math.Min(offsetMax, newOffsetMax);
if (_offset.Value < offsetMin || _offset.Value > offsetMax)
{
// the old offset was offrange, throw it away and use new one
_offset = new ExponentialMovingAverage(PingWindowSize);
_offset.Add(newOffset);
}
else if (newOffset >= offsetMin || newOffset <= offsetMax)
{
// new offset looks reasonable, add to the average
_offset.Add(newOffset);
}
}
// executed at the server when we receive a ping message
// reply with a pong containing the time from the client
// and time from the server
internal void OnServerPing(INetworkConnection conn, NetworkPingMessage msg)
{
if (logger.LogEnabled())
{
logger.Log("OnPingServerMessage conn=" + conn);
}
var pongMsg = new NetworkPongMessage
{
clientTime = msg.clientTime,
serverTime = LocalTime()
};
conn.Send(pongMsg, Channel.Unreliable);
}