diff --git a/README.md b/README.md
index 7f975ea..c1e3daf 100644
--- a/README.md
+++ b/README.md
@@ -41,11 +41,10 @@ CN=CA openssl req -config openssl.cnf -x509 -new -nodes -key ca.key -sha256 -day
 # create example client CSR for testing (check openssl.cnf against "psk" file)
 CN=rotuer openssl req -config openssl.cnf -newkey rsa:2048 -nodes -keyout client.key -out client.csr
 
-# start the server
-bin/certifix
+# build and start the server
+nix-build && result/bin/certifix  --challenge-password psk  --certificate ca.crt --private-key ca.key localhost:19613
 
 # send it
-
 curl -v -H 'content-type: application/x-pem-file' --data-binary @client.csr  http://localhost:8201/sign
 ```
 
diff --git a/main.fnl b/main.fnl
index 6321494..ee52592 100644
--- a/main.fnl
+++ b/main.fnl
@@ -53,14 +53,14 @@
     (assoc (parse-args rest) :private-key (slurp f))
     ["--challenge-password" f & rest]
     (assoc (parse-args rest) :challenge-password (read-line f))
-    [peer] { : peer }
+    [bind-address] { : bind-address }
     _ {}))
 
 (local options
        (doto
            (parse-args arg)
          (case
-             {: certificate : private-key : challenge-password : peer}
+             {: certificate : private-key : challenge-password : bind-address}
            true
            _
            (assert nil "missing required command line params"))))
@@ -100,24 +100,30 @@
   (let [hdrs (out:get_headers)
         method (hdrs:get ":method")
         path (or (hdrs:get ":path") "/")]
-    (print :path path)
     (case path
       "/sign"
       (handle-sign-csr out)
       _
       (send-error out 404 "not found"))))
 
+;; ncall is the opposite of pcall: "non-protected call"
+(macro ncall [f]
+  `(case ,f
+     ok# ok#
+     (nil err#) (error err#)))
 
 (fn new-server []
-  (server.listen
-            {
-             :host :localhost
-             :port 8201
-             :onstream on-stream
-             }))
+  (let [(addr port) (string.match options.bind-address "(.+):(%d+)$")]
+    (case (server.listen
+           {
+            :host addr
+            :port (tonumber port)
+            :onstream on-stream
+            })
+      f (doto f (print))
+      (nil e) (error e))))
 
-
-(doto (new-server)
-  (: :listen)
+(let [s (new-server)]
+  (ncall (s:listen))
   (print "server ready")
-  (: :loop))
+  (ncall (s:loop)))