I received a good suggestion from an other source and I've downloaded a viewer that allows to edit .hws that is HDF view (http://www.hdfgroup.org/hdf-java-html/hdfview/). In this viewer is possible to see that the bit names contained into the file aren't sequential, so the channels identifier became higher than the real number of the channels contained into the .hws.
So, to extract all the name I've changed H5G Find-Open Numbered Groups.vi with a for loop instead of the while settings more than 1000 loops even if I have an hws made by 170 signals.