'Oi, tudo bem?' is an extremely common greeting, often used as both hello and how are you. 'Tudo bem?' on its own can also be a question or a response. For farewells, 'tchau' is universally understood and used.
- Oi, tudo bem?
- Hi, how are you? / Hi, is everything okay?
- Tudo bem?
- How are you? / Is everything okay?
- tchau
- bye
