ssh_base.rb

  class SshBase

    attr_accessor :host, :username, :password, :timeout

    class SSHException < Exception; end;

    # Callbacks storage for Channel Execute Callbacks
    class ChannelExecCallBacks
      attr_accessor :on_success, :on_failure, :on_data, :on_extended_data, :on_close
    end

    def initialize
      @timeout = 1200 # 20 minutes 
    end

    # Initiate SSH Connection
    def start(method_to_send)
      init_ssh { |ssh| channel_open ssh, method_to_send }
    end

    # Open an SSH Channel
    def channel_open(ssh, method_to_send)
      ssh.open_channel { |channel| method_to_send(channel) }
    end              

    # Execute SSH CMDs on an open Channel
    def channel_exec(channel, cmd)
      
      channel.exec(cmd) do |ch, success|

        channel_exec_call_backs = ChannelExecCallBacks.new
        yield channel_exec_call_backs

        channel_exec_call_backs.tap do |call_back|
          send call_back.on_success if success && !call_back.on_success.nil?
          send call_back.on_failure unless success && call_back.on_failure.nil?
          channel.on_data { |ch, data| send call_back.on_data, ch, data }                   unless call_back.on_data.nil?
          channel.on_extended_data { |ch, data| send call_back.on_extended_data, ch, data } unless call_back.on_extended_data.nil?
          channel.on_close { |ch, data| send call_back.on_close, ch, data }                 unless call_back.on_close.nil?
        end

      end
      
    end

    private

      def init_ssh

        begin
          @ssh ||= ::Net::SSH.start("#{@host}", "#{@username}", { :password => "#{@password}", :timeout => @timeout }) do |ssh|
            yield ssh
            ssh.loop
          end
        rescue => e
          raise new SSHException("SSH Exception: #{e.message}")
        end

      end          

  end