door guard vs hall porter

door guard and hall porter both are nouns.

Word	Noun	Adjective	Verb	Adverb
door guard	Yes	No	No	No
hall porter	Yes	No	No	No

As nouns, door guard and hall porter are synonyms defined as:

Other synonyms of door guard include doorkeeper, doorman, gatekeeper, ostiary, porter.

door guard (noun)	hall porter (noun)
someone who guards an entrance	someone who guards an entrance