## connection flow
```mermaid
sequenceDiagram
autonumber
participant C as Client
participant S as Server
Note over C,S: create tcp connection phase
C->>S: establish tcp connection(wrap tls, connect via proxy)
Note over C,S: http protocol upgrade phase | handle by "Handshake" trait
C-->>S: http upgrade
S-->>C: 101 upgrade response
Note over C,S: websocket protocol phase
loop until one peer sends "Close" frame, frame encode/decode by "FrameCodec" trait
C--)S: write frame
S--)C: read frame
end
Note right of C: assume client wants to quit
C--)S: close frame
alt receive close from server
S--)C: close reponse
else read response timeout
C-xC: exit
end
Note over C,S: close tcp connection
```