gistfile1.cs

public class UdpTraceListener : TraceListener
{
	// For 3.5/2 you can use a List but the class is no longer thread safe.
	//private Stack<string> _messageBuffer;

	private UdpClient _udpClient;
	private ConcurrentStack<string> _messageBuffer;
	private string _loggerName;

	private static readonly string _xmlPrefix = "log4j";
	private static readonly string _xmlNamespace = "http://jakarta.apache.org/log4j/";

	public override bool IsThreadSafe
	{
		get
		{
			return true;
		}
	}

	public UdpTraceListener()
		: this("localhost", 7071, "UdpTraceListener")
	{

	}

	public UdpTraceListener(string host, int port, string loggerName)
	{
		_loggerName = loggerName;
		_messageBuffer = new ConcurrentStack<string>();
		_udpClient = new UdpClient();
		_udpClient.Connect(host, port);
	}

	public override void Write(string message)
	{
		Write(message, "info");
	}

	public override void WriteLine(string message)
	{
		Write(message, "info");
		Flush();
	}

	public override void WriteLine(string message, string category)
	{
		_messageBuffer.Push(GetEventXml(message, category));
		Flush();
	}

	public override void Write(string message, string category)
	{
		_messageBuffer.Push(GetEventXml(message, category));
	}

	private string GetEventXml(string message, string category)
	{
		// The format:
		//<log4j:event logger="{LOGGER}" level="{LEVEL}" thread="{THREAD}" timestamp="{TIMESTAMP}">
		//  <log4j:message><![CDATA[{ERROR}]]></log4j:message>
		//  <log4j:NDC><![CDATA[{MESSAGE}]]></log4j:NDC>
		//  <log4j:throwable><![CDATA[{EXCEPTION}]]></log4j:throwable>
		//  <log4j:locationInfo class="org.apache.log4j.chainsaw.Generator" method="run" file="Generator.java" line="94"/>
		//  <log4j:properties>
		//	<log4j:data name="log4jmachinename" value="{SOURCE}"/>
		//	<log4j:data name="log4japp" value="{APP}"/>
		//  </log4j:properties>
		//</log4j:event>

		string level = "INFO";
		if (string.IsNullOrEmpty(category))
			category = "info";

		switch (category.ToLower())
		{
			case "fatal":
				level = "FATAL";
				break;

			case "warning":
			case "warn":
				level = "WARN";
				break;

			case "error":
				level = "ERROR";
				break;

			case "debug":
				level = "DEBUG";
				break;

			case "trace":
				level = "TRACE";
				break;

			default:
				break;
		}

		StringBuilder builder = new StringBuilder();

		XmlWriterSettings settings = new XmlWriterSettings();
		settings.OmitXmlDeclaration = true;

		XmlWriter writer = XmlWriter.Create(builder, settings);
		WriteLog4jElement(writer, "event");
		writer.WriteAttributeString("logger", _loggerName);
		writer.WriteAttributeString("level", level);
		writer.WriteAttributeString("thread", Thread.CurrentThread.ManagedThreadId.ToString());
		writer.WriteAttributeString("timestamp", XmlConvert.ToString(ConvertToUnixTimestamp(DateTime.Now)));

		WriteLog4jElement(writer, "message");
		writer.WriteCData(RemoveInvalidXmlChars(message));
		writer.WriteEndElement();
		WriteLog4jElementString(writer, "NDC", "");
		WriteLog4jElementString(writer, "throwable", "");

		WriteLog4jElement(writer, "locationInfo");
		writer.WriteAttributeString("class", "");
		writer.WriteAttributeString("run", "");
		writer.WriteAttributeString("file", "");
		writer.WriteAttributeString("line", "1");
		writer.WriteEndElement();

		WriteLog4jElement(writer, "properties");
		WriteLog4jElement(writer, "data");
		writer.WriteAttributeString("name", "log4jmachinename");
		writer.WriteAttributeString("value", Environment.MachineName);
		writer.WriteEndElement();

		WriteLog4jElement(writer, "data");
		writer.WriteAttributeString("name", "log4japp");
		writer.WriteAttributeString("value", Assembly.GetCallingAssembly().FullName);
		writer.WriteEndElement();
		writer.WriteEndElement();

		writer.WriteEndElement();

		writer.Flush();
		return builder.ToString();
	}

	private string RemoveInvalidXmlChars(string text)
	{
		var validXmlChars = text.Where(x => XmlConvert.IsXmlChar(x)).ToArray();
		return new string(validXmlChars);
	}

	private void WriteLog4jElement(XmlWriter writer, string name)
	{
		writer.WriteStartElement(_xmlPrefix, name, _xmlNamespace);
	}

	private void WriteLog4jElementString(XmlWriter writer, string name, string value)
	{
		writer.WriteElementString(_xmlPrefix, name, _xmlNamespace, value);
	}

	private double ConvertToUnixTimestamp(DateTime date)
	{
		DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, 0);
		TimeSpan sinceEpoch = date.ToUniversalTime() - epoch;
		return Math.Floor(sinceEpoch.TotalMilliseconds);
	}

	public override void Flush()
	{
		foreach (string xmlMessage in _messageBuffer)
		{
			byte[] payload = Encoding.UTF8.GetBytes(xmlMessage);
			_udpClient.Send(payload, payload.Length);
		}

		_messageBuffer.Clear();
		base.Flush();
	}

	protected override void Dispose(bool disposing)
	{
		Flush();
		_udpClient.Close();

		base.Dispose(disposing);
	}

	public override void TraceEvent(TraceEventCache eventCache, string source, TraceEventType eventType, int id, string format, params object[] args)
	{
		switch (eventType)
		{
			case TraceEventType.Critical:
			case TraceEventType.Error:
				WriteLine(string.Format(format, args), "error");
				break;

			case TraceEventType.Verbose:
				WriteLine(string.Format(format, args), "debug");
				break;

			case TraceEventType.Warning:
				WriteLine(string.Format(format, args), "warn");
				break;

			case TraceEventType.Information:
			case TraceEventType.Resume:
			case TraceEventType.Start:
			case TraceEventType.Stop:
			case TraceEventType.Suspend:
			case TraceEventType.Transfer:
			default:
				WriteLine(string.Format(format, args), "error");
				break;
		}
	}
}