diff --git a/src/build/run.cr b/src/build/run.cr
index a7cee4f..89ed74e 100644
--- a/src/build/run.cr
+++ b/src/build/run.cr
@@ -5,6 +5,7 @@ require "socket"
 
 require "./module"
 require "./config"
+require "../common/network"
 
 module DocMachine::Build
   class Run
@@ -19,7 +20,6 @@ module DocMachine::Build
       @process = nil
     end
 
-
     # cleanup environment
     # create directories
     # setup permissions
@@ -32,22 +32,6 @@ module DocMachine::Build
       self._avoid_duplicates() unless @config.enable_multiple
     end
 
-    private def _find_port(port_base)
-      (port_base..65535).each do |port|
-        return port if _port_available?(port)
-      end
-      raise "No port available"
-    end
-
-    private def _port_available?(port)
-      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
       Log.info { "Multiple Instances: stopping duplicate containers (for #{@docker_name})" }
       docker_cid = %x{docker ps -f "name=#{@docker_name}" -q}.strip
@@ -161,7 +145,7 @@ module DocMachine::Build
       ## Detect docs
       if Dir.exists?("#{@config.data_dir}/docs")
         Log.info { "Docs: detected docs directory." }
-        mkdocs_port = _find_port(@config.port)
+        mkdocs_port = Network.find_port(@config.port)
         docker_opt_mkdocs_port = ["-p", "#{mkdocs_port}:5100"]
         docker_opts.concat docker_opt_mkdocs_port
         Log.notice { "Using port #{mkdocs_port} for docs" }
@@ -173,7 +157,7 @@ module DocMachine::Build
       ## Detect slides
       if Dir.exists?("#{@config.data_dir}/slides")
         Log.info { "Slides: detected slides directory." }
-        marp_port = _find_port(@config.port+100)
+        marp_port = Network.find_port(@config.port+100)
         docker_opt_marp_port = ["-p", "#{marp_port}:5200"]
         docker_opts.concat docker_opt_marp_port 
         Log.info { "Slides: Adding option to command line (#{docker_opt_marp_port})" }
diff --git a/src/common/network.cr b/src/common/network.cr
new file mode 100644
index 0000000..eee02e8
--- /dev/null
+++ b/src/common/network.cr
@@ -0,0 +1,19 @@
+
+class Network
+
+  def self.find_port(port_base)
+      (port_base..65535).each do |port|
+        return port if self.port_available?(port)
+      end
+      raise "No port available"
+    end
+
+  def self.port_available?(port)
+      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
+end