How do you define friends?

To me friends are you share things and support each other when needed or you try your best to help out each other. But in London, I find many so called friends are more acquaintance, they like to meet you to go out dinning and drinking, but when you want to chat or a shoulder to cry on, they just not there, but they when need yours they expect you there.

So tell me how do you define friends nowadays?