Add UDP port checker (rudimentary)

lib/watchmonkey_cli.rb

@@ -37,6 +37,7 @@
 require "watchmonkey_cli/checkers/ssl_expiration"
 require "watchmonkey_cli/checkers/tcp_port"
 require "watchmonkey_cli/checkers/ts3_license"
+require "watchmonkey_cli/checkers/udp_port"
 require "watchmonkey_cli/checkers/unix_defaults"
 require "watchmonkey_cli/checkers/unix_df"
 require "watchmonkey_cli/checkers/unix_file_exists"

lib/watchmonkey_cli/application/configuration.tpl

@@ -73,6 +73,24 @@ tcp_port "ftp.example.com", 21, message: "FTP offline"
 tcp_port :my_server, 21, message: "FTP offline"
 
 
+# -----
+# UDP port
+# -----
+# Attempts to establish a UDP connection to a given port.
+# NOTE: We send a message and attempt to receive a response.
+#       If the port is closed we get an IO exception and assume the port to be unreachable.
+#       If the port is open we most likely don't get ANY response and when the timeout
+#       is reached we assume the port to be reachable. This is not an exact check.
+# Host might be :local/SSH connection/String(IP/DNS)
+# Available options:
+#
+#   message    Error message when connection cannot be established
+#   timeout    Timeout in seconds to wait for a response (default = 2 seconds - false/nil = 1 hour)
+#
+udp_port "example.com", 9987, message: "Teamspeak offline"
+udp_port :my_server, 9987, message: "Teamspeak offline"
+
+
 # -----
 # FTP availability
 # -----

lib/watchmonkey_cli/checkers/udp_port.rb

@@ -0,0 +1,34 @@
+module WatchmonkeyCli
+  module Checkers
+    class UdpPort < Checker
+      self.checker_name = "udp_port"
+
+      def enqueue host, port, opts = {}
+        opts = { message: "Port #{port} (UDP) is not reachable!", timeout: 2 }.merge(opts)
+        host = app.fetch_connection(:loopback, :local) if !host || host == :local
+        host = app.fetch_connection(:ssh, host) if host.is_a?(Symbol)
+        app.enqueue(self, host, port, opts)
+      end
+
+      def check! result, host, port, opts = {}
+        result.result = port_open?(host.is_a?(String) ? host : host.is_a?(WatchmonkeyCli::LoopbackConnection) ? "127.0.0.1" : host.opts[:host_name] || host.opts[:host] || host.opts[:ip], port, opts)
+        result.error! "#{opts[:message]}" unless result.result
+      end
+
+      def port_open?(ip, port, opts = {})
+        Timeout::timeout(opts[:timeout] ? opts[:timeout] : 3600) do
+          s = UDPSocket.new
+          s.connect(ip, port)
+          s.send "aaa", 0
+          s.recv(1)
+          s.close
+        end
+        true
+      rescue Errno::ECONNREFUSED, Errno::EHOSTUNREACH
+        return false
+      rescue Timeout::Error
+        return true
+      end
+    end
+  end
+end