ViaThinkSoft CodeLib
This article is in:
CodeLib → Programming aids → C#
using System;
using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;
using System.Threading;
using System.Net.Sockets;
using System.Net;
using System.Linq;
namespace ConsoleApp6
{
class Program
{
public class AtomzeitAsync
{
public struct Atomzeit
{
public string server;
public DateTime zeit;
}
protected static DateTime GetNetworkTime(string ntpServer, bool utc = false)
{
// https://stackoverflow.com/questions/1193955/how-to-query-an-ntp-server-using-c
// NTP message size - 16 bytes of the digest (RFC 2030)
var ntpData = new byte[48];
//Setting the Leap Indicator, Version Number and Mode values
ntpData[0] = 0x1B; //LI = 0 (no warning), VN = 3 (IPv4 only), Mode = 3 (Client Mode)
var addresses = Dns.GetHostEntry(ntpServer).AddressList;
//The UDP port number assigned to NTP is 123
var ipEndPoint = new IPEndPoint(addresses[0], 123);
//NTP uses UDP
using (var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp))
{
socket.Connect(ipEndPoint);
//Stops code hang if NTP is blocked
socket.ReceiveTimeout = 3000;
socket.Send(ntpData);
socket.Receive(ntpData);
socket.Close();
}
//Offset to get to the "Transmit Timestamp" field (time at which the reply
//departed the server for the client, in 64-bit timestamp format."
const byte serverReplyTime = 40;
//Get the seconds part
ulong intPart = BitConverter.ToUInt32(ntpData, serverReplyTime);
//Get the seconds fraction
ulong fractPart = BitConverter.ToUInt32(ntpData, serverReplyTime + 4);
//Convert From big-endian to little-endian
intPart = SwapEndianness(intPart);
fractPart = SwapEndianness(fractPart);
var milliseconds = (intPart * 1000) + ((fractPart * 1000) / 0x100000000L);
//**UTC** time
var networkDateTime = (new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc)).AddMilliseconds((long)milliseconds);
return utc ? networkDateTime : networkDateTime.ToLocalTime();
}
private static uint SwapEndianness(ulong x)
{
// https://stackoverflow.com/questions/1193955/how-to-query-an-ntp-server-using-c
// stackoverflow.com/a/3294698/162671
return (uint)(((x & 0x000000ff) << 24) +
((x & 0x0000ff00) << 8) +
((x & 0x00ff0000) >> 8) +
((x & 0xff000000) >> 24));
}
static AtomzeitAsync()
{
string zeitServerFile = "TimeserverNTP.txt";
if (File.Exists(zeitServerFile))
{
bool containsSomething = false;
var lines = File.ReadAllLines(zeitServerFile);
foreach (var line in lines)
{
if (line.Trim() == "") continue;
if (line.Trim().Substring(0, 1) == "#") continue;
containsSomething = true;
break;
}
if (containsSomething)
{
Array.Resize(ref servers, 0);
foreach (var line in lines)
{
if (line.Trim() == "") continue;
if (line.Trim().Substring(0, 1) == "#") continue;
Array.Resize(ref servers, servers.Length + 1);
servers[servers.Length - 1] = line.Trim();
}
}
}
else
{
string[] dummyList = { };
File.WriteAllLines(zeitServerFile, dummyList.ToList());
}
}
public static string[] servers = {
"ptbtime1.ptb.de",
"ptbtime2.ptb.de",
"ptbtime3.ptb.de"
};
public static Atomzeit? GetAtomzeit(int timeout = 1000)
{
List<Task<Atomzeit>> tasks = new List<Task<Atomzeit>>();
int bakWorkerThreads = 0;
int bakCompletionPortThreads = 0;
ThreadPool.GetMinThreads(out bakWorkerThreads, out bakCompletionPortThreads);
ThreadPool.SetMinThreads(bakWorkerThreads + servers.Length, bakCompletionPortThreads + servers.Length);
try
{
for (int i = 0; i < servers.Length; i++)
{
tasks.Add(GetFileLengthsAsync(servers[i], false));
}
Thread.Sleep(timeout);
for (int ctr = 0; ctr < tasks.Count; ctr++)
{
if (tasks[ctr].Status == TaskStatus.RanToCompletion)
{
return tasks[ctr].Result;
}
}
return null;
}
finally
{
ThreadPool.SetMinThreads(bakWorkerThreads, bakCompletionPortThreads);
}
}
private static Task<Atomzeit> GetFileLengthsAsync(string serverIp, bool utc)
{
return Task.Factory.StartNew(() =>
{
// Variable für Fehlermeldungen
string errors = null;
try
{
Atomzeit res = new Atomzeit();
res.server = serverIp;
res.zeit = GetNetworkTime(serverIp, utc);
return res;
}
catch (Exception ex)
{
// Fehler dokumentieren
if (errors != null) errors += "\r\n";
errors += "Fehler bei der Abfrage von '" +
serverIp + ": " + ex.Message;
}
// Wenn die Methode hier ankommt, sind bei allen Abfragen
// Fehler aufgetreten, also eine Ausnahme werfen
throw new Exception(errors);
});
}
}
public static void Main()
{
AtomzeitAsync.Atomzeit? az = AtomzeitAsync.GetAtomzeit();
if (az == null)
{
Console.WriteLine("Atomzeit konnte nicht ermittelt werden");
}
else
{
Console.WriteLine("Atomzeit: {0} gemeldet durch {1}", ((AtomzeitAsync.Atomzeit)az).zeit, ((AtomzeitAsync.Atomzeit)az).server);
}
Console.ReadLine();
}
}
}Daniel Marschall
ViaThinkSoft Co-Founder
ViaThinkSoft Co-Founder