def size(filename)
      voidcmd("TYPE I")
      resp = sendcmd("SIZE " + filename)
      if resp[0, 3] != "213" 
	raise FTPReplyError, resp
      end
      return resp[3..-1].strip.to_i
    end
def size(filename)
      voidcmd("TYPE I")
      resp = sendcmd("SIZE " + filename)
      if resp[0, 3] != "213" 
	raise FTPReplyError, resp
      end
      return resp[3..-1].strip.to_i
    end
Returns the size of the given (remote) filename.