code: def start_client(self, host, port=5001, protocol='TCP', timeout=5,
                       parallel=None, bandwidth=None):
          
          cmd = ['iperf',  '-c', host, '-p', str(port), '-t', str(timeout)]
          if not (protocol, 'UDP'):
              cmd.append('-u')
          if parallel:
              cmd.extend(['-P', str(parallel)])
          if bandwidth:
              cmd.extend(['-b', '%sM' % bandwidth])
          stdcode, stdout, stderr = utils.execute_wait(cmd)
          if (not stdcode) or (not stderr):
              out_dict = stdout.split('\n')
              if not out_dict[-1]:
                  out_dict.pop()
              out_data = out_dict[-1].split()
              data = dict()
              data['Bandwidth'] = out_data[-2] + ' ' + out_data[-1]
              data['Transfer'] = out_data[-4] + ' ' + out_data[-3]
              data['Interval'] = out_data[-6]
              return data
          raise Exception('Start iperf failed, please check on the node.')
docs: iperf -D -c host -t 60