SntpClient failure notification

[trailway]

The SntpClient class is notifying failures multiple times. This can be reproduced by pulling the network cable from machine. I added the following check to avoid this:

    public void BeginGetDate(Action<DateTime> getTime, Action failure)
    {
        _index += 1;
        if (_hosts.Length <= _index)
        {
            if (_hosts.Length == _index)
            {
                failure();
            }
            return;
        }

I suspect that there may be a deeper problem here but the fix isn't obvious to me.

[ayende]

The actual reason for the failure isn't that interesting. It can be a network cable not connected, bad WIFI connection,etc.

We want to handle all errors in the same manner

[trailway]

I think that the problem is that MaybeOperationTimeout is not checking to see if a socket was created:

    private void MaybeOperationTimeout(object state, bool timedOut)
    {
        if (timedOut == false)
            return;

        var theState = (State)state;
        try
        {
            theState.Socket?.Close();
        }

This results in an unnecessary retry because Dns.BeginGetHostAddresses is failing (it takes longer than 1/2 second) and there is no socket.

[trailway]

The problem is that it is notifying the failure multiple times. I think
that it should either call the success or failure function once.

I think that the root cause of the problem that MaybeOperationTimeout is
called from RegisterWaitForTimeout which is called from BeginGetDate and
there is a timeout but no socket. Dns.BeginGetHostAddresses throws an
exception (it takes a while) which causes a recursive BeginGetDate. The
null socket also causes a BeginGetDate as well.

What I did was:

1. Only notify 1 time
2. Test if the socket is null in MaybeOperationTimeout

Thanks for contributing the code.

On Thu, Aug 27, 2015 at 12:18 AM, Ayende Rahien [email protected]
wrote:

The actual reason for the failure isn't that interesting. It can be a
network cable not connected, bad WIFI connection,etc.

We want to handle all errors in the same manner

—
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#12 (comment)
.

[ayende]

Can you show your changes? I'm not sure that I can follow from the description.

[trailway]

See attached code.

On Fri, Aug 28, 2015 at 5:53 AM, Ayende Rahien [email protected]
wrote:

Can you show your changes? I'm not sure that I can follow from the
description.

—
Reply to this email directly or view it on GitHub
#12 (comment)
.

using System;
using System.CodeDom.Compiler;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace LicensingShared
{
///

/// Provides support for asynchronously acquiring the current time
/// via well known sources for time.
/// </summary>


/// <remarks>
/// This code is taken from <a href="https://github.com/ayende/rhino-licensing">rhino-licensing</a>.
/// See <a href="https://github.com/ayende/rhino-licensing/blob/master/license.txt">copyright notice</a>.
/// Minor corrections where made to the code as a result of testing.
/// </remarks>
[GeneratedCode(@"rhino-licensing", @"08/25/2015")]
internal class SntpClient
{
    private const byte SntpDataLength = 48;
    private readonly string[] _hosts;
    private int _index = -1;

    public SntpClient(string[] hosts)
    {
        _hosts = hosts;
    }

    private static bool GetIsServerMode(byte[] sntpData)
    {
        return (sntpData[0] & 0x7) == 4 /* server mode */;
    }

    private static DateTime GetTransmitTimestamp(byte[] sntpData)
    {
        var milliSeconds = GetMilliSeconds(sntpData, 40);
        return ComputeDate(milliSeconds);
    }

    private static DateTime ComputeDate(ulong milliseconds)
    {
        return new DateTime(1900, 1, 1).Add(TimeSpan.FromMilliseconds(milliseconds));
    }

    private static ulong GetMilliSeconds(byte[] sntpData, byte offset)
    {
        ulong intpart = 0, fractpart = 0;

        for (var i = 0; i <= 3; i++)
        {
            intpart = 256 * intpart + sntpData[offset + i];
        }
        for (var i = 4; i <= 7; i++)
        {
            fractpart = 256 * fractpart + sntpData[offset + i];
        }
        var milliseconds = intpart * 1000 + (fractpart * 1000) / 0x100000000L;
        return milliseconds;
    }

    public void BeginGetDate(Action<DateTime> getTime, Action failure)
    {
        _index += 1;
        if (_hosts.Length <= _index)
        {
            if (_hosts.Length == _index)
            {
                failure();
            }
            return;
        }
        try
        {
            var host = _hosts[_index];
            var state = new State(null, null, getTime, failure);
            var result = Dns.BeginGetHostAddresses(host, EndGetHostAddress, state);
            RegisterWaitForTimeout(state, result);
        }
        catch (Exception)
        {
            // retry, recursion stops at the end of the hosts
            BeginGetDate(getTime, failure);
        }
    }

    private void EndGetHostAddress(IAsyncResult asyncResult)
    {
        var state = (State)asyncResult.AsyncState;
        try
        {
            var addresses = Dns.EndGetHostAddresses(asyncResult);
            var endPoint = new IPEndPoint(addresses[0], 123);

            var socket = new UdpClient();
            socket.Connect(endPoint);
            socket.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 500);
            socket.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.SendTimeout, 500);
            var sntpData = new byte[SntpDataLength];
            sntpData[0] = 0x1B; // version = 4 & mode = 3 (client)

            var newState = new State(socket, endPoint, state.GetTime, state.Failure);
            var result = socket.BeginSend(sntpData, sntpData.Length, EndSend, newState);
            RegisterWaitForTimeout(newState, result);
        }
        catch (Exception)
        {
            // retry, recursion stops at the end of the hosts
            BeginGetDate(state.GetTime, state.Failure);
        }
    }

    private void RegisterWaitForTimeout(State newState, IAsyncResult result)
    {
        if (result != null)
        {
            ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, MaybeOperationTimeout, newState, 500,
                true);
        }
    }

    private void MaybeOperationTimeout(object state, bool timedOut)
    {
        if (timedOut == false)
            return;

        var theState = (State)state;
        try
        {
            theState.Socket?.Close();
        }
        catch (Exception)
        {
            // retry, recursion stops at the end of the hosts
            BeginGetDate(theState.GetTime, theState.Failure);
        }
    }

    private void EndSend(IAsyncResult ar)
    {
        var state = (State)ar.AsyncState;
        try
        {
            state.Socket.EndSend(ar);
            var result = state.Socket.BeginReceive(EndReceive, state);
            RegisterWaitForTimeout(state, result);
        }
        catch
        {
            state.Socket.Close();
            BeginGetDate(state.GetTime, state.Failure);
        }
    }

    private void EndReceive(IAsyncResult ar)
    {
        var state = (State)ar.AsyncState;
        try
        {
            var endPoint = state.EndPoint;
            var sntpData = state.Socket.EndReceive(ar, ref endPoint);
            if (IsResponseValid(sntpData) == false)
            {
                state.Failure();
                return;
            }
            var transmitTimestamp = GetTransmitTimestamp(sntpData);
            state.GetTime(transmitTimestamp);
        }
        catch
        {
            BeginGetDate(state.GetTime, state.Failure);
        }
        finally
        {
            state.Socket.Close();
        }
    }

    private bool IsResponseValid(byte[] sntpData)
    {
        return sntpData.Length >= SntpDataLength && GetIsServerMode(sntpData);
    }

    #region Nested type: State

    private class State
    {
        public State(UdpClient socket, IPEndPoint endPoint, Action<DateTime> getTime, Action failure)
        {
            Socket = socket;
            EndPoint = endPoint;
            GetTime = getTime;
            Failure = failure;
        }

        public UdpClient Socket { get; private set; }

        public Action<DateTime> GetTime { get; private set; }

        public Action Failure { get; private set; }

        public IPEndPoint EndPoint { get; private set; }
    }

    #endregion
}

}

[ayende]

I can't really read this. Can you send this as a PR, that way it would be
much easier to see the changes.

*Hibernating Rhinos Ltd *

Oren Eini* l CEO l *Mobile: + 972-52-548-6969

Office: +972-4-622-7811 *l *Fax: +972-153-4-622-7811

On Fri, Aug 28, 2015 at 4:54 PM, trailway [email protected] wrote:

See attached code.

On Fri, Aug 28, 2015 at 5:53 AM, Ayende Rahien [email protected]
wrote:

Can you show your changes? I'm not sure that I can follow from the
description.

—
Reply to this email directly or view it on GitHub
<
#12 (comment)

.

using System;
using System.CodeDom.Compiler;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace LicensingShared
{
///

/// Provides support for asynchronously acquiring the current time
/// via well known sources for time.
///

///
/// This code is taken from rhino-licensing.
/// See copyright
notice.
/// Minor corrections where made to the code as a result of testing.
///
[GeneratedCode(@"rhino-licensing", @"08/25/2015")]
internal class SntpClient
{
private const byte SntpDataLength = 48;
private readonly string[] _hosts;
private int _index = -1;

public SntpClient(string[] hosts)
{
_hosts = hosts;
}

private static bool GetIsServerMode(byte[] sntpData)
{
return (sntpData[0] & 0x7) == 4 /* server mode */;
}

private static DateTime GetTransmitTimestamp(byte[] sntpData)
{
var milliSeconds = GetMilliSeconds(sntpData, 40);
return ComputeDate(milliSeconds);
}

private static DateTime ComputeDate(ulong milliseconds)
{
return new DateTime(1900, 1,
1).Add(TimeSpan.FromMilliseconds(milliseconds));
}

private static ulong GetMilliSeconds(byte[] sntpData, byte offset)
{
ulong intpart = 0, fractpart = 0;

for (var i = 0; i <= 3; i++)
{
intpart = 256 * intpart + sntpData[offset + i];
}
for (var i = 4; i <= 7; i++)
{
fractpart = 256 * fractpart + sntpData[offset + i];
}
var milliseconds = intpart * 1000 + (fractpart * 1000) / 0x100000000L;
return milliseconds;
}

public void BeginGetDate(Action getTime, Action failure)
{
_index += 1;
if (_hosts.Length <= _index)
{
if (_hosts.Length == _index)
{
failure();
}
return;
}
try
{
var host = _hosts[_index];
var state = new State(null, null, getTime, failure);
var result = Dns.BeginGetHostAddresses(host, EndGetHostAddress, state);
RegisterWaitForTimeout(state, result);
}
catch (Exception)
{
// retry, recursion stops at the end of the hosts
BeginGetDate(getTime, failure);
}
}

private void EndGetHostAddress(IAsyncResult asyncResult)
{
var state = (State)asyncResult.AsyncState;
try
{
var addresses = Dns.EndGetHostAddresses(asyncResult);
var endPoint = new IPEndPoint(addresses[0], 123);

var socket = new UdpClient();
socket.Connect(endPoint);
socket.Client.SetSocketOption(SocketOptionLevel.Socket,
SocketOptionName.ReceiveTimeout, 500);
socket.Client.SetSocketOption(SocketOptionLevel.Socket,
SocketOptionName.SendTimeout, 500);
var sntpData = new byte[SntpDataLength];
sntpData[0] = 0x1B; // version = 4 & mode = 3 (client)

var newState = new State(socket, endPoint, state.GetTime, state.Failure);
var result = socket.BeginSend(sntpData, sntpData.Length, EndSend,
newState);
RegisterWaitForTimeout(newState, result);
}
catch (Exception)
{
// retry, recursion stops at the end of the hosts
BeginGetDate(state.GetTime, state.Failure);
}
}

private void RegisterWaitForTimeout(State newState, IAsyncResult result)
{
if (result != null)
{
ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle,
MaybeOperationTimeout, newState, 500,
true);
}
}

private void MaybeOperationTimeout(object state, bool timedOut)
{
if (timedOut == false)
return;

var theState = (State)state;
try
{
theState.Socket?.Close();
}
catch (Exception)
{
// retry, recursion stops at the end of the hosts
BeginGetDate(theState.GetTime, theState.Failure);
}
}

private void EndSend(IAsyncResult ar)
{
var state = (State)ar.AsyncState;
try
{
state.Socket.EndSend(ar);
var result = state.Socket.BeginReceive(EndReceive, state);
RegisterWaitForTimeout(state, result);
}
catch
{
state.Socket.Close();
BeginGetDate(state.GetTime, state.Failure);
}
}

private void EndReceive(IAsyncResult ar)
{
var state = (State)ar.AsyncState;
try
{
var endPoint = state.EndPoint;
var sntpData = state.Socket.EndReceive(ar, ref endPoint);
if (IsResponseValid(sntpData) == false)
{
state.Failure();
return;
}
var transmitTimestamp = GetTransmitTimestamp(sntpData);
state.GetTime(transmitTimestamp);
}
catch
{
BeginGetDate(state.GetTime, state.Failure);
}
finally
{
state.Socket.Close();
}
}

private bool IsResponseValid(byte[] sntpData)
{
return sntpData.Length >= SntpDataLength && GetIsServerMode(sntpData);
}

#region Nested type: State

private class State
{
public State(UdpClient socket, IPEndPoint endPoint, Action
getTime, Action failure)
{
Socket = socket;
EndPoint = endPoint;
GetTime = getTime;
Failure = failure;
}

public UdpClient Socket { get; private set; }

public Action GetTime { get; private set; }

public Action Failure { get; private set; }

public IPEndPoint EndPoint { get; private set; }
}

#endregion
}
}

—
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#12 (comment)
.

[trailway]

Done.

My first pull request.

On Fri, Aug 28, 2015 at 11:07 AM, Ayende Rahien [email protected]
wrote:

I can't really read this. Can you send this as a PR, that way it would be
much easier to see the changes.

*Hibernating Rhinos Ltd *

Oren Eini* l CEO l *Mobile: + 972-52-548-6969

Office: +972-4-622-7811 *l *Fax: +972-153-4-622-7811

On Fri, Aug 28, 2015 at 4:54 PM, trailway [email protected]
wrote:

See attached code.

On Fri, Aug 28, 2015 at 5:53 AM, Ayende Rahien <[email protected]

wrote:

Can you show your changes? I'm not sure that I can follow from the
description.

—
Reply to this email directly or view it on GitHub
<

#12 (comment)

.

using System;
using System.CodeDom.Compiler;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace LicensingShared
{
///

/// Provides support for asynchronously acquiring the current time
/// via well known sources for time.
///

///
/// This code is taken from rhino-licensing.
/// See copyright
notice.
/// Minor corrections where made to the code as a result of testing.
///
[GeneratedCode(@"rhino-licensing", @"08/25/2015")]
internal class SntpClient
{
private const byte SntpDataLength = 48;
private readonly string[] _hosts;
private int _index = -1;

public SntpClient(string[] hosts)
{
_hosts = hosts;
}

private static bool GetIsServerMode(byte[] sntpData)
{
return (sntpData[0] & 0x7) == 4 /* server mode */;
}

private static DateTime GetTransmitTimestamp(byte[] sntpData)
{
var milliSeconds = GetMilliSeconds(sntpData, 40);
return ComputeDate(milliSeconds);
}

private static DateTime ComputeDate(ulong milliseconds)
{
return new DateTime(1900, 1,
1).Add(TimeSpan.FromMilliseconds(milliseconds));
}

private static ulong GetMilliSeconds(byte[] sntpData, byte offset)
{
ulong intpart = 0, fractpart = 0;

for (var i = 0; i <= 3; i++)
{
intpart = 256 * intpart + sntpData[offset + i];
}
for (var i = 4; i <= 7; i++)
{
fractpart = 256 * fractpart + sntpData[offset + i];
}
var milliseconds = intpart * 1000 + (fractpart * 1000) / 0x100000000L;
return milliseconds;
}

public void BeginGetDate(Action getTime, Action failure)
{
_index += 1;
if (_hosts.Length <= _index)
{
if (_hosts.Length == _index)
{
failure();
}
return;
}
try
{
var host = _hosts[_index];
var state = new State(null, null, getTime, failure);
var result = Dns.BeginGetHostAddresses(host, EndGetHostAddress, state);
RegisterWaitForTimeout(state, result);
}
catch (Exception)
{
// retry, recursion stops at the end of the hosts
BeginGetDate(getTime, failure);
}
}

private void EndGetHostAddress(IAsyncResult asyncResult)
{
var state = (State)asyncResult.AsyncState;
try
{
var addresses = Dns.EndGetHostAddresses(asyncResult);
var endPoint = new IPEndPoint(addresses[0], 123);

var socket = new UdpClient();
socket.Connect(endPoint);
socket.Client.SetSocketOption(SocketOptionLevel.Socket,
SocketOptionName.ReceiveTimeout, 500);
socket.Client.SetSocketOption(SocketOptionLevel.Socket,
SocketOptionName.SendTimeout, 500);
var sntpData = new byte[SntpDataLength];
sntpData[0] = 0x1B; // version = 4 & mode = 3 (client)

var newState = new State(socket, endPoint, state.GetTime, state.Failure);
var result = socket.BeginSend(sntpData, sntpData.Length, EndSend,
newState);
RegisterWaitForTimeout(newState, result);
}
catch (Exception)
{
// retry, recursion stops at the end of the hosts
BeginGetDate(state.GetTime, state.Failure);
}
}

private void RegisterWaitForTimeout(State newState, IAsyncResult result)
{
if (result != null)
{
ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle,
MaybeOperationTimeout, newState, 500,
true);
}
}

private void MaybeOperationTimeout(object state, bool timedOut)
{
if (timedOut == false)
return;

var theState = (State)state;
try
{
theState.Socket?.Close();
}
catch (Exception)
{
// retry, recursion stops at the end of the hosts
BeginGetDate(theState.GetTime, theState.Failure);
}
}

private void EndSend(IAsyncResult ar)
{
var state = (State)ar.AsyncState;
try
{
state.Socket.EndSend(ar);
var result = state.Socket.BeginReceive(EndReceive, state);
RegisterWaitForTimeout(state, result);
}
catch
{
state.Socket.Close();
BeginGetDate(state.GetTime, state.Failure);
}
}

private void EndReceive(IAsyncResult ar)
{
var state = (State)ar.AsyncState;
try
{
var endPoint = state.EndPoint;
var sntpData = state.Socket.EndReceive(ar, ref endPoint);
if (IsResponseValid(sntpData) == false)
{
state.Failure();
return;
}
var transmitTimestamp = GetTransmitTimestamp(sntpData);
state.GetTime(transmitTimestamp);
}
catch
{
BeginGetDate(state.GetTime, state.Failure);
}
finally
{
state.Socket.Close();
}
}

private bool IsResponseValid(byte[] sntpData)
{
return sntpData.Length >= SntpDataLength && GetIsServerMode(sntpData);
}

#region Nested type: State

private class State
{
public State(UdpClient socket, IPEndPoint endPoint, Action
getTime, Action failure)
{
Socket = socket;
EndPoint = endPoint;
GetTime = getTime;
Failure = failure;
}

public UdpClient Socket { get; private set; }

public Action GetTime { get; private set; }

public Action Failure { get; private set; }

public IPEndPoint EndPoint { get; private set; }
}

#endregion
}
}

—
Reply to this email directly or view it on GitHub
<
#12 (comment)

.

—
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#12 (comment)
.

[ayende]

Thanks, I mreged it.

*Hibernating Rhinos Ltd *

Oren Eini* l CEO l *Mobile: + 972-52-548-6969

Office: +972-4-622-7811 *l *Fax: +972-153-4-622-7811

On Fri, Aug 28, 2015 at 8:46 PM, trailway [email protected] wrote:

Done.

My first pull request.

On Fri, Aug 28, 2015 at 11:07 AM, Ayende Rahien [email protected]
wrote:

I can't really read this. Can you send this as a PR, that way it would be
much easier to see the changes.

*Hibernating Rhinos Ltd *

Oren Eini* l CEO l *Mobile: + 972-52-548-6969

Office: +972-4-622-7811 *l *Fax: +972-153-4-622-7811

On Fri, Aug 28, 2015 at 4:54 PM, trailway [email protected]
wrote:

See attached code.

On Fri, Aug 28, 2015 at 5:53 AM, Ayende Rahien <
[email protected]

wrote:

Can you show your changes? I'm not sure that I can follow from the
description.

—
Reply to this email directly or view it on GitHub
<

#12 (comment)

.

using System;
using System.CodeDom.Compiler;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace LicensingShared
{
///

/// Provides support for asynchronously acquiring the current time
/// via well known sources for time.
///

///
/// This code is taken from rhino-licensing.
/// See copyright
notice.
/// Minor corrections where made to the code as a result of testing.
///
[GeneratedCode(@"rhino-licensing", @"08/25/2015")]
internal class SntpClient
{
private const byte SntpDataLength = 48;
private readonly string[] _hosts;
private int _index = -1;

public SntpClient(string[] hosts)
{
_hosts = hosts;
}

private static bool GetIsServerMode(byte[] sntpData)
{
return (sntpData[0] & 0x7) == 4 /* server mode */;
}

private static DateTime GetTransmitTimestamp(byte[] sntpData)
{
var milliSeconds = GetMilliSeconds(sntpData, 40);
return ComputeDate(milliSeconds);
}

private static DateTime ComputeDate(ulong milliseconds)
{
return new DateTime(1900, 1,
1).Add(TimeSpan.FromMilliseconds(milliseconds));
}

private static ulong GetMilliSeconds(byte[] sntpData, byte offset)
{
ulong intpart = 0, fractpart = 0;

for (var i = 0; i <= 3; i++)
{
intpart = 256 * intpart + sntpData[offset + i];
}
for (var i = 4; i <= 7; i++)
{
fractpart = 256 * fractpart + sntpData[offset + i];
}
var milliseconds = intpart * 1000 + (fractpart * 1000) / 0x100000000L;
return milliseconds;
}

public void BeginGetDate(Action getTime, Action failure)
{
_index += 1;
if (_hosts.Length <= _index)
{
if (_hosts.Length == _index)
{
failure();
}
return;
}
try
{
var host = _hosts[_index];
var state = new State(null, null, getTime, failure);
var result = Dns.BeginGetHostAddresses(host, EndGetHostAddress, state);
RegisterWaitForTimeout(state, result);
}
catch (Exception)
{
// retry, recursion stops at the end of the hosts
BeginGetDate(getTime, failure);
}
}

private void EndGetHostAddress(IAsyncResult asyncResult)
{
var state = (State)asyncResult.AsyncState;
try
{
var addresses = Dns.EndGetHostAddresses(asyncResult);
var endPoint = new IPEndPoint(addresses[0], 123);

var socket = new UdpClient();
socket.Connect(endPoint);
socket.Client.SetSocketOption(SocketOptionLevel.Socket,
SocketOptionName.ReceiveTimeout, 500);
socket.Client.SetSocketOption(SocketOptionLevel.Socket,
SocketOptionName.SendTimeout, 500);
var sntpData = new byte[SntpDataLength];
sntpData[0] = 0x1B; // version = 4 & mode = 3 (client)

var newState = new State(socket, endPoint, state.GetTime,
state.Failure);
var result = socket.BeginSend(sntpData, sntpData.Length, EndSend,
newState);
RegisterWaitForTimeout(newState, result);
}
catch (Exception)
{
// retry, recursion stops at the end of the hosts
BeginGetDate(state.GetTime, state.Failure);
}
}

private void RegisterWaitForTimeout(State newState, IAsyncResult
result)
{
if (result != null)
{
ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle,
MaybeOperationTimeout, newState, 500,
true);
}
}

private void MaybeOperationTimeout(object state, bool timedOut)
{
if (timedOut == false)
return;

var theState = (State)state;
try
{
theState.Socket?.Close();
}
catch (Exception)
{
// retry, recursion stops at the end of the hosts
BeginGetDate(theState.GetTime, theState.Failure);
}
}

private void EndSend(IAsyncResult ar)
{
var state = (State)ar.AsyncState;
try
{
state.Socket.EndSend(ar);
var result = state.Socket.BeginReceive(EndReceive, state);
RegisterWaitForTimeout(state, result);
}
catch
{
state.Socket.Close();
BeginGetDate(state.GetTime, state.Failure);
}
}

private void EndReceive(IAsyncResult ar)
{
var state = (State)ar.AsyncState;
try
{
var endPoint = state.EndPoint;
var sntpData = state.Socket.EndReceive(ar, ref endPoint);
if (IsResponseValid(sntpData) == false)
{
state.Failure();
return;
}
var transmitTimestamp = GetTransmitTimestamp(sntpData);
state.GetTime(transmitTimestamp);
}
catch
{
BeginGetDate(state.GetTime, state.Failure);
}
finally
{
state.Socket.Close();
}
}

private bool IsResponseValid(byte[] sntpData)
{
return sntpData.Length >= SntpDataLength && GetIsServerMode(sntpData);
}

#region Nested type: State

private class State
{
public State(UdpClient socket, IPEndPoint endPoint, Action
getTime, Action failure)
{
Socket = socket;
EndPoint = endPoint;
GetTime = getTime;
Failure = failure;
}

public UdpClient Socket { get; private set; }

public Action GetTime { get; private set; }

public Action Failure { get; private set; }

public IPEndPoint EndPoint { get; private set; }
}

#endregion
}
}

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