Fixed to where server errors happen before the fork.

ls_echo.rb

@@ -53,9 +53,8 @@ if not directory.directory?
     raise ArgumentError, "Path #{DIRECTORY} does not represent a valid directory."
 end
 
-
+server = TCPServer.new port
 fork do
-  server = TCPServer.new port
   Process.daemon
   loop do
     Thread.start(server.accept) do |client|