code: function () {
  
  	var currTime = new Date();
  	var overtime = (SR.Settings.INTERVAL_STAT_REPORT * 2);
  
  	// remove servers no longer reporting
  	for (var serverID in SR.Report.servers) {
  		var stat = SR.Report.servers[serverID];
  		
  		if (!stat || !stat.reportedTime)
  			continue;
  		
  		// server considered dead
  		if (currTime - stat.reportedTime > overtime) {
  			var ip_port = stat.server.IP + ':' + stat.server.port;
  			LOG.sys(ip_port + ' overtime: ' + overtime + ' last: ' + stat.reportedTime);
  
  			LOG.error('server: ' + ip_port + ' (' + stat.server.type + ') not responding after ' + overtime + ' ms, mark dead...', 'SR.Monitor');
  			SR.Report.removeStat(serverID);
  			
  			// recycle port if it's from a local server
  			if (stat.server.IP === SR.Settings.SERVER_INFO.IP) {
  				LOG.warn('server is a local server, re-cycle its ports...', 'SR.Monitor');
  				l_recyclePort(stat.ports);
  			}
  		}
  	}
  }
docs: internal functions  periodic checking liveness of app servers