Today, one student asked what is correct:
Answer: Both options are absolutely correct 
, although “der Socken” is only used in dialectal German. 
Do you have other examples of different use of gender of the same word? 
I’m not that sure, but I think “das Pyjama” and “der Pyjama” 
. Once I read and article that said that many words from English usually have two articles.
Both are correct
But you can also say “der Schlafanzug” 
I had a similar issue regarding die / das Cola. While discussing this with my student, some other examples came to mind – das/die Nutella, die/der Ikea, der/die/das Spezi [not sure if this drink is popular outside Bavaria – it’s 50/50 Cola and Sprite/Limo]. But all the examples I could come up with seemed to be brand names in one way or another…