diff --git a/src/build/run.cr b/src/build/run.cr
index 0bbf523..f95591c 100644
--- a/src/build/run.cr
+++ b/src/build/run.cr
@@ -1,6 +1,7 @@
 
 require "path"
 require "file_utils"
+require "socket"
 
 require "./module"
 require "./config"
@@ -38,7 +39,12 @@ module DocMachine::Build
     end
 
     private def _port_available?(port)
-      true
+      sock = Socket.new(Socket::Family::INET, Socket::Type::STREAM)
+      sock.bind(Socket::IPAddress.new("0.0.0.0", port))
+      sock.close
+      return true
+    rescue ex : Socket::BindError
+      return false
     end
 
     private def _avoid_duplicates