Msg Type,Description,Reference
0,HANDSHAKE,[RFC7574]
1,DATA,[RFC7574]
2,ACK,[RFC7574]
3,HAVE,[RFC7574]
4,INTEGRITY,[RFC7574]
5,PEX_RESv4,[RFC7574]
6,PEX_REQ,[RFC7574]
7,SIGNED_INTEGRITY,[RFC7574]
8,REQUEST,[RFC7574]
9,CANCEL,[RFC7574]
10,CHOKE,[RFC7574]
11,UNCHOKE,[RFC7574]
12,PEX_RESv6,[RFC7574]
13,PEX_REScert,[RFC7574]
14-254,Unassigned,
255,Reserved,[RFC7574]