diff --git a/crystal/makefile.user b/crystal/makefile.user
index 8d2a41f..5ea91cd 100644
--- a/crystal/makefile.user
+++ b/crystal/makefile.user
@@ -1,8 +1,12 @@
-WS_SERVICE  ?= 127.0.0.1:8080
+WS_PORT     ?= 8080
+WS_SERVICE  ?= 127.0.0.1:$(WS_PORT)
+
+WS_TARGET_SERVICE ?= pong
+WS_TARGET         ?= unix:/tmp/.libipc-run/$(WS_TARGET_SERVICE)
 init-websocket-tcpd:
 	@# '-b' binary, '-E' quit on end-of-file, 'ws-l' websocket URI to listen
 	@# each connection is redirected to last parameter
-	websocat -b -E ws-l:$(WS_SERVICE) unix:/tmp/.libipc-run/pong
+	websocat -b -E ws-l:$(WS_SERVICE) $(WS_TARGET)
 
 init-websocket-client:
 	@# websocat -b -E tcp-l:127.0.0.1:9000 ws://127.0.0.1:9999