fixup

Author: sam-github

doc/api/net.markdown

@@ -228,9 +228,10 @@ shown below.
 
 Stops the server from accepting new connections and keeps existing
 connections. This function is asynchronous, the server is finally
-closed when all connections are ended and the server emits a `'close'`
-event.  The last parameter `callback` will be added as an listener for the
-['close'][] event.
+closed when all connections are ended and the server emits a ['close'][] event.
+The optional `callback` will be called once the `'close'` event occurs. Unlike
+that event, it will be called with an Error as its only argument if the server
+was not open when it was closed.
 
 ### server.address()