code: public void enqueue(TargetTransportPort port, Command command)
     {
        long lun = command.getNexus().getLogicalUnitNumber();
  
        if (lun < 0)
        {
           try
           {
              Task task = this.taskFactory.getInstance(port, command);
              assert task != null : "improper task factory implementation returned null task";
              this.targetTaskSet.offer(task); // non-blocking, sends any errors to transport port
              if (_logger.isDebugEnabled())
                 _logger.debug("successfully enqueued target command with TaskRouter: " + command);
           }
           catch (IllegalRequestException e)
           {
              _logger.error("error when parsing command: " + e);
              port.writeResponse(command.getNexus(), command.getCommandReferenceNumber(),
                    Status.CHECK_CONDITION, ByteBuffer.wrap(e.encode()));
           }
        }
        else if (logicalUnitMap.containsKey(lun))
        {
           logicalUnitMap.get(lun).enqueue(port, command);
           if (_logger.isDebugEnabled())
              _logger.debug("successfully enqueued command to logical unit with TaskRouter: "
                    + command);
        }
        else
        {
           port.writeResponse(command.getNexus(), command.getCommandReferenceNumber(),
                 Status.CHECK_CONDITION,
                 ByteBuffer.wrap((new LogicalUnitNotSupportedException()).encode()));
        }
     }
docs: TaskRouter implementation