diff --git a/src/baguette-crystal-base.cr b/src/baguette-crystal-base.cr
index 634c9a1..029046f 100644
--- a/src/baguette-crystal-base.cr
+++ b/src/baguette-crystal-base.cr
@@ -50,19 +50,20 @@ class Baguette::Configuration
 	end
 
 	class IPC < Base
+		enum MESSAGE
+			TIMER
+			CONNECTION
+			DISCONNECTION
+			EXTERNAL  # extra socket
+			RX
+			TX
+			SWITCH
+			ERROR
+			EXCEPTION
+		end
+
 		property ipc_timer                  : Int32 = 30_000 # 30 seconds.
-
-		property print_ipc_timer            : Bool  = false
-		property print_ipc_connection       : Bool  = false
-		property print_ipc_disconnection    : Bool  = false
-		property print_ipc_extra_socket     : Bool  = false
-		property print_ipc_message_received : Bool  = false
-		property print_ipc_message_sent     : Bool  = false
-		property print_ipc_switch           : Bool  = false
-		property print_ipc_error            : Bool  = true
-		property print_ipc_exception        : Bool  = true
-		property print_keepalive            : Bool  = false
-
+		property ipc_messages_to_show       : Array(IPC::MESSAGE) = [MESSAGE::ERROR, MESSAGE::EXCEPTION]
 		property verbosity                  : Int32 = 4
 
 		def initialize
@@ -125,49 +126,94 @@ class Baguette::Configuration
 	end
 end
 
+# `Baguette::Log` is a library to display information.
+# A filename can be given to write logs in a file.
 class Baguette::Log
-	# FIXME: Use log files.
 	# FIXME: def log(), that puts stuff as-is in the logs.
 
+	# Name of the file.
+	class_property log_path : String? = nil
+
+	enum LOGTYPE
+		DEBUG   = 5
+		INFO    = 4
+		TITLE   = 3
+		WARNING = 2
+		ERROR   = 1
+	end
+
+	def self.now() : String
+		Time.local.to_s("%Y-%m-%d_%H:%M:%S")
+	end
+
+	def self.write_log_fancy(io : IO, logtype : LOGTYPE, text)
+		case logtype
+		when .debug?
+			io.<<(self.now).<<(" :: ".colorize(:cyan)).<<(text.colorize(:cyan)).<<("\n")
+		when .info?
+			io.<<(self.now).<<(" :: ".colorize(:blue)).<<(text.colorize(:white)).<<("\n")
+		when .title?
+			io.<<(self.now).<<(" |> ".colorize(:blue).bright).<<(text.colorize(:white).bright).<<("\n")
+		when .warning?
+			io.<<(self.now).<<(" :: ".colorize(:yellow).bright).<<(text.colorize(:yellow)).<<("\n")
+		when .error?
+			io.<<(self.now).<<(" !! ".colorize(:red).bright).<<(text.colorize(:red)).<<("\n")
+		end
+	end
+
+	def self.write_log_plain(io : IO, logtype : LOGTYPE, text)
+		case logtype
+		when .debug?
+			io.<<(self.now).<<(" (debug) ").<<(text).<<("\n")
+		when .info?
+			io.<<(self.now).<<(" (info) ").<<(text).<<("\n")
+		when .title?
+			io.<<(self.now).<<(" (title) ").<<(text).<<("\n")
+		when .warning?
+			io.<<(self.now).<<(" (warning) ").<<(text).<<("\n")
+		when .error?
+			io.<<(self.now).<<(" (error) ").<<(text).<<("\n")
+		end
+	end
+
+	def self.write_log(logtype : LOGTYPE, text)
+		if path = @@log_path
+			File.open path, "a" do |io|
+				self.write_log_plain io, logtype, text
+			end
+
+			# In case the thing we want to print is important, put it on the screen too.
+			if logtype <= LOGTYPE::WARNING
+				self.write_log_fancy STDERR, logtype, text
+			end
+		else
+			if logtype <= LOGTYPE::WARNING
+				self.write_log_fancy STDERR, logtype, text
+			else
+				self.write_log_fancy STDOUT, logtype, text
+			end
+		end
+	end
+
 	def self.debug(text)
 		return unless Baguette::Context.verbosity > 3
-		STDERR
-			.<<(":: ".colorize(:cyan))
-			.<<(text.colorize(:cyan))
-			.<<("\n")
-		STDERR.flush
+		self.write_log LOGTYPE::DEBUG, text
 	end
 	def self.info(text)
 		return unless Baguette::Context.verbosity > 2
-		STDOUT
-			.<<(":: ".colorize(:blue))
-			.<<(text.colorize(:white))
-			.<<("\n")
-		STDOUT.flush
+		self.write_log LOGTYPE::INFO, text
 	end
 	def self.title(text)
 		return unless Baguette::Context.verbosity > 2
-		STDOUT
-			.<<("|> ".colorize(:blue).bright)
-			.<<(text.colorize(:white).bright)
-			.<<("\n")
-		STDOUT.flush
+		self.write_log LOGTYPE::TITLE, text
 	end
 	def self.warning(text)
 		return unless Baguette::Context.verbosity > 1
-		STDERR
-			.<<(":: ".colorize(:yellow).bright)
-			.<<(text.colorize(:yellow))
-			.<<("\n")
-		STDERR.flush
+		self.write_log LOGTYPE::WARNING, text
 	end
 	def self.error(text)
 		return unless Baguette::Context.verbosity > 0
-		STDERR
-			.<<("!! ".colorize(:red).bright)
-			.<<(text.colorize(:red))
-			.<<("\n")
-		STDERR.flush
+		self.write_log LOGTYPE::ERROR, text
 	end
 end