def on_writable
      begin
        @_write_buffer.write_to(@_io)
      rescue Errno::EINTR
        return

      # SystemCallError catches Errno::EPIPE & Errno::ECONNRESET amongst others.
      rescue SystemCallError, IOError, SocketError
        return close
      end

      if @_write_buffer.empty?
        disable_write_watcher
        on_write_complete
      end
    end
def on_writable
      begin
        @_write_buffer.write_to(@_io)
      rescue Errno::EINTR
        return

      # SystemCallError catches Errno::EPIPE & Errno::ECONNRESET amongst others.
      rescue SystemCallError, IOError, SocketError
        return close
      end

      if @_write_buffer.empty?
        disable_write_watcher
        on_write_complete
      end
    end
Write the contents of the output buffer