Multistream-select

Multistream-select is the "main" protocol of libp2p. Whenever a connection opens between two peers, it starts talking in multistream-select.

The purpose of multistream-select is to choose which protocol we are going to use. As soon as both sides agree on a given protocol, the socket immediately starts using it and multistream is no longer relevant.

However note that multistream-select is also sometimes used on top of another protocol such as secio or multiplex. For example, two hosts can use multistream-select to decide to use secio, then use multistream-select again (wrapped inside secio) to decide to use multiplex, then use multistream-select one more time (wrapped inside secio and multiplex) to decide to use the final actual protocol.