module Async::IO::Peer

def connected?

May return false positive, but won't return false negative.
Is it likely that the socket is still connected? 
def connected?
	return false if @io.closed?
	
	# If we can wait for the socket to become readable, we know that the socket may still be open.
	result = to_io.recv_nonblock(1, MSG_PEEK, exception: false)
	
	# No data was available - newer Ruby can return nil instead of empty string:
	return false if result.nil?
	
	# Either there was some data available, or we can wait to see if there is data avaialble.
	return !result.empty? || result == :wait_readable
	
rescue Errno::ECONNRESET
	# This might be thrown by recv_nonblock.
	return false
end

def eof 

def eof
	!connected?
end

def eof? 

def eof?
	!connected?
end

def protocol 

def protocol
	self.local_address.protocol
end

def sync 

def sync
	case self.protocol
	when IPPROTO_TCP
		self.getsockopt(IPPROTO_TCP, TCP_NODELAY).bool
	else
		true
	end && super
end

def sync=(value)

Best effort to set *_NODELAY if it makes sense. Swallows errors where possible. 
def sync=(value)
	super
	
	case self.protocol
	when 0, IPPROTO_TCP
		self.setsockopt(IPPROTO_TCP, TCP_NODELAY, value ? 1 : 0)
	else
		Console.logger.warn(self) {"Unsure how to sync=#{value} for #{self.protocol}!"}
	end
rescue Errno::EINVAL
	# On Darwin, sometimes occurs when the connection is not yet fully formed. Empirically, TCP_NODELAY is enabled despite this result.
rescue Errno::EOPNOTSUPP
	# Some platforms may simply not support the operation.
	# Console.logger.warn(self) {"Unable to set sync=#{value}!"}
end

def type 

def type
	self.local_address.socktype
end