Not a lot, in effect, if by 'social' you mean 'sociable'. A single person is not usually called 'social' - but you do hear things like 'Homo sapiens is a social animal' (where it means 'participating in social contacts/networks').
But it rather depends what you mean by 'communicative'; the prefix 'com-' (cum - 'with') suggests to me that there's a sender and a receiver involved. But sometimes 'communicative' is just used to mean talkative, voluble or opinionated, and in that case someone can impart information without being sociable.)
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