public MongoClient abrirConexion()
	{		
		if(mongo != null)
		{
			return mongo;			
		}
		
		try 
		{
			mongo = new MongoClient(host, puerto);
			db = mongo.getDB(nombredb);
		} 
		catch (UnknownHostException e) 
		{
			e.printStackTrace();
		}
		
		return mongo;
	}