flow.uml

@startuml
participant PeerA as a
participant PeerB as b

note over a, b
	11.4 Initialize
end note

a <-> b: Handshake message
a <-> b: Bitfield message
alt receive Bitfield message
	
	note left
	Length is the number of fileblock.
	end note

	
	a -> a: updateBitfield state
	
	a -> b: Interest/Not Interest message
	note left
	compare to check if there is interested block
	end note
end alt

alt receive Interesed/Not Interested message
	a -> a: record into interested list
end alt

loop every p(m) seconds
	a -> a: 
	note left
	select K fastest download rate in interested list as preferred neighbor list
	(randomly one in the rest as optimistically neighbor)
	If already unchoked the peer, don't send unchoke message
	If already have all field, randomly select k + 1 peers
	end note
	
	alt b is in prefered list and optimistically neighbor
		a -> b: unchocked
	else
		a -> b: chocked
	end alt

end loop


alt receive unchoked
	
	a -> a: compare to find if there is still having interesting block
	alt true
		a -> b: request random one interested piece, which not request
	else false
		a -> b: Not interested message
	
	end alt
	
	
else receive choke
end alt

alt received request
	 a -> b: send required Piece
	 
end alt

alt received Piece
	a -> a: updateBitfield state
	
	alt
		a -> b: request random one interested piece, which not request
		note left
		compare to find if there is still having interesting block
		if true randomly select one block
		end note
	else
		a -> b: Not interested
		b -> b: record into interested list
	end alt

	a -> b: have Piece number
	
end alt

alt receive have message
	a -> a: updateBitfield state
	a -> b: Interest/Not Interest message
	note left
	compare to check if there is interested block
	end note
end alt


@enduml