IsPortOpen utility

lib/vagrant/util/is_port_open.rb

@@ -0,0 +1,38 @@
+require "socket"
+require "timeout"
+
+module Vagrant
+  module Util
+    # Contains the method {#is_ruby_open?} to check if a port is open
+    # (listening) or closed (not in use). This method isn't completely
+    # fool-proof, but it works enough of the time to be useful.
+    module IsPortOpen
+      # Checks if a port is open (listening) on a given host and port.
+      #
+      # @param [String] host Hostname or IP address.
+      # @param [Integer] port Port to check.
+      # @return [Boolean] `true` if the port is open (listening), `false`
+      #   otherwise.
+      def is_port_open?(host, port)
+        # We wrap this in a timeout because once in awhile the TCPSocket
+        # _will_ hang, but this signals that the port is closed.
+        Timeout.timeout(1) do
+          # Attempt to make a connection
+          s = TCPSocket.new(host, port)
+
+          # A connection was made! Properly clean up the socket, not caring
+          # at all if any exception is raised, because we already know the
+          # result.
+          s.close rescue nil
+
+          # The port is open if we reached this point, since we were able
+          # to connect.
+          return true
+        end
+      rescue Timeout::Error, Errno::ECONNREFUSED, Errno::EHOSTUNREACH
+        # Any of the above exceptions signal that the port is closed.
+        return false
+      end
+    end
+  end
+end

test/unit/vagrant/util/is_port_open_test.rb

@@ -0,0 +1,53 @@
+require File.expand_path("../../../base", __FILE__)
+
+require "socket"
+
+require "vagrant/util/is_port_open"
+
+describe Vagrant::Util::IsPortOpen do
+  let(:klass) do
+    Class.new do
+      extend Vagrant::Util::IsPortOpen
+    end
+  end
+
+  let(:open_port)   { 52811 }
+  let(:closed_port) { 52811 }
+
+  it "should report open ports" do
+    # Start a thread which listens on a port
+    thr = Thread.new do
+      server = TCPServer.new(open_port)
+      Thread.current[:running] = true
+
+      # Wait until we're told to die
+      Thread.current[:die]     = false
+      while !Thread.current[:die]
+        Thread.pass
+      end
+
+      # Die!
+      server.close
+    end
+
+    # Wait until the server is running
+    while !thr[:running]
+      Thread.pass
+    end
+
+    # Verify that we report the port is open
+    klass.is_port_open?("localhost", open_port).should be
+
+    # Kill the thread
+    thr[:die] = true
+    thr.join
+  end
+
+  it "should report closed ports" do
+    # This CAN fail, since port 52811 might actually be in use, but I'm
+    # not sure what to do except choose some random port and hope for the
+    # best, really.
+    klass.is_port_open?("localhost", closed_port).should_not be
+  end
+end
+