diff --git a/lib/knot/protocol.rb b/lib/knot/protocol.rb
index 3ba7b2b..784c81c 100644
--- a/lib/knot/protocol.rb
+++ b/lib/knot/protocol.rb
@@ -53,7 +53,7 @@ module Knot::Protocol::Type
 end
 
 #class Knot::KnotC
-#	attr_accessor :debug, :binary
+#	attr_accessor :binary
 #
 #	def initialize path = nil, binary: nil
 #   @path = path
@@ -141,10 +141,9 @@ module Knot::Protocol::Idx
 end
 
 class Knot::Protocol
-	attr_reader :sock, :conf, :zones
-	attr_accessor :debug
+	attr_reader :sock, :conf, :zones, :logger
 
-	def initialize path_or_sock = nil
+	def initialize path_or_sock = nil, logger: nil
 		case path_or_sock
 		when String, Pathname
 			@sock = UNIXSocket.new path_or_sock.to_s
@@ -153,7 +152,7 @@ class Knot::Protocol
 		when nil
 			@sock = UNIXSocket.new '/run/knot/knot.sock'
 		end
-		@debug = false
+		@logger = logger || Logger.new(STDERR)
 		@conf = Knot::Conf.new self
 		@zones = Hash.new {|h, zone| h[zone] = Knot::Zone.new zone, self }
 	end
@@ -170,7 +169,10 @@ class Knot::Protocol
 		end
 		sock.write [3].pack( 'c')
 		sock.flush
-		STDERR.puts( {send: data, _: s}.inspect)  if @debug
+		if 0 >= @logger.sev_threshold
+			@logger.debug "send data #{data.inspect}"
+			@logger.debug "send raw  #{data.inspect}"
+		end
 		rsock.write s
 		rsock.flush
 	end
@@ -200,7 +202,7 @@ class Knot::Protocol
 	def rcv sock: nil
 		ret, r = [], nil
 		sock = sock || @sock
-		sock = RecordIO.new sock  if @debug
+		sock = RecordIO.new sock  if 0 >= @logger.sev_threshold
 		loop do
 			t = sock.unpack1 'c'
 			case t
@@ -217,7 +219,10 @@ class Knot::Protocol
 			end
 		end
 	ensure
-		STDERR.puts( {rcvd: ret, _: sock.str}.inspect)  if @debug
+		if RecordIO === sock
+			@logger.debug "rcvd raw  #{sock.str.inspect}"
+			@logger.debug "rcvd data #{ret.inspect}"
+		end
 		ret
 	end