To set up the target in the configuration file, use the following syntax:

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> 
  <targets> 
    <target name="viewer" xsi:type="NLogViewer" address="ucp://localhost:4000"/> 
  </targets> 
  <rules> 
    <logger name="*" minlevel="Debug" writeTo="viewer"/> 
  </rules> 
</nlog> 

This assumes just one target and a single rule. More configuration options are described here.

To set up the log target programmatically use code like this:

using NLog; 
using NLog.Targets; 
 
class Example 
{ 
    static void Main(string[] args) 
    { 
        NLogViewerTarget target = new NLogViewerTarget(); 
        target.Address = "udp://localhost:4000"; 
 
        NLog.Config.SimpleConfigurator.ConfigureForTargetLogging(target, LogLevel.Debug); 
 
        Logger logger = LogManager.GetLogger("Example"); 
        logger.Trace("log message 1"); 
        logger.Debug("log message 2"); 
        logger.Info("log message 3"); 
        logger.Warn("log message 4"); 
        logger.Error("log message 5"); 
        logger.Fatal("log message 6"); 
    } 
}

NOTE: If your receiver application is ever likely to be off-line, don't use TCP protocol or you'll get TCP timeouts and your application will crawl. Either switch to UDP transport or use AsyncWrapper target so that your application threads will not be blocked by the timing-out connection attempts.