How can you know about an unknown person, who just being your friend?

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I have just invite few persons at a place for a get-together, and meet them.but when i approch them to generate a relation in between us then I am shoked they never told and communicate to each other. I think to know any one the best way is communication but if a persone who accept u as a FRIEND but he/she never response u then wht u to do to know them........? plz answer it comes to such a very big probelem for me..... help..........