为什么从带有EAI_FAIL模块的Pycom WiPy板发送HTTP时会引发"[Errno 202] _urequest“异常？

Question

上下文

我有一个Pycom WiPy板运行一些Python代码。代码使用.NET模块向_urequest web发出HTTP请求。

问题

发送HTTP请求时，将引发[Errno 202] EAI_FAIL异常。由于请求在循环中每10秒发送一次，这种情况在一次又一次发生。

代码

Wifi客户端，连接本地wifi并获得因特网接入。

import json
import time
from network import WLAN

# Wifi client singleton
wifiClient = None

def initWifiClient():
    global wifiClient
    wifiClient = WifiClient()

def getWifiClient():
    global wifiClient
    return wifiClient

class WifiClient:

    wifi = None
    lastWifiConnectAttempt = None

    def __init__(self):
        self.wifi = WLAN(mode=WLAN.STA)
        pass

    def connect(self):
        if not self.__readyForNewWifiConnectAttempt():
            print("Not ready yet for new WIFI connect attempt.")
            self.__printSecondsLeftToNextConnectAttempt()
            return

        print("Trying to connect WIFI.")
        try:
            self.lastWifiConnectAttempt = time.time()
            with open('wifi.json') as json_file:
                wifiJson = json.load(json_file)

                self.wifi.connect(ssid=wifiJson['ssid'], auth=(WLAN.WPA2, wifiJson['password']), timeout=30000)

                # Add connection timeout handler to prevent timeout exception crash.
                self.wifi.callback(WLAN.SMART_CONF_TIMEOUT, handler=self.__onWifiConnectTimeout)

                pass
        except Exception as e:
            self.lastWifiConnectAttempt = None
            print (e)
            pass

    def __readyForNewWifiConnectAttempt(self):
        if self.lastWifiConnectAttempt == None:
            return True
        
        return (time.time() - self.lastWifiConnectAttempt) > 42

    def __onWifiConnectTimeout(self, args):
        self.lastWifiConnectAttempt = None
        pass

    # For debugging
    def __printSecondsLeftToNextConnectAttempt(self):
        secondsLeft = 43 - (time.time() - self.lastWifiConnectAttempt)
        if secondsLeft < 0:
            secondsLeft = 0

        print("Seconds left to be ready for next WIFI connect attempt: " +  str(secondsLeft))

Web调用方/客户端代码，用于向web api发送不同调用的助手模块：

这个mdoule运行后台工作循环，它进行api调用并捕获[Errno 202] EAI_FAIL异常。

from machine import Timer
from hardware import web, unit
from events import commands as cmd
from util import weblog
import ujson
import pycom
import gc
from hardware.wifi_client import getWifiClient

# globals for this file
_background_timer = None
_background_app = None



def get_client():
  client = web.Client()
  client.base_url = "..."
  # client.base_url = "..."
  return client

def send_data(): 
  print ("sending data")
  client = get_client()

  client.headers['Content-Type'] = 'application/json'

  # client.headers['Accept'] = '*/*'
  # client.headers['User-Agent'] = 'PostmanRuntime/7.28.4'
  # client.headers['Host'] = '...'
  # client.headers['Connection'] = 'keep-alive'

  p = cmd.Measure()

  data = {
    'uuid' : unit.ID,
    'value' : round(p, 1),
    'measured': "1970-01-01T00:00:00.000Z"
  }

  response = client.post('ApiMethod', data)
  print (response.text)
  pass


def background_work(o):
  global _background_app
  global wifiClient

  try:
    pycom.rgbled(0)
    gc.collect()

    mfree = gc.mem_free()

    print ("Memfree: " + str(mfree))
    if (getWifiClient().wifi.isconnected()):

      if (mfree < 1000000):
        weblog.warning("Memory low: %d", mfree)
        print("Memory low: %d", mfree)

      send_data()
    
      app = _background_app
      fetch_data(app)
      pycom.rgbled(0x002f00)
       
    else:
      pycom.rgbled(0x2F)
      print ("Not connected to WIFI")
      getWifiClient().connect()

  except Exception as e:
    pycom.rgbled(0x2f0000)
    print("send exception")
    print(e)
    
    pass
  pass

def stop_background():
  global _background_timer
  
  if _background_timer:
    _background_timer.cancel()
    _background_timer = None

  pass

def start_background(app):
  global _background_timer, _background_app

  stop_background()

  _background_app = app
  _background_timer = Timer.Alarm(background_work, s=10, periodic=True)
  pass

HTTP客户端，对api进行HTTP调用：

import _urequest as ureq


class Client:

  def __init__(self):
    self.headers = {}
    self.base_url = ""
    pass

  ...

  def post(self, url, payload):
    print(self.base_url)
    print(self.base_url + url)
    return ureq.post(self.base_url + url, headers = self.headers, json = payload)

  ...

  def base(self, url):
    self.base_url = url

控制台输出

sending data
send exception
[Errno 202] EAI_FAIL
Memfree: 2527712
sending data
send exception
[Errno 202] EAI_FAIL
Memfree: 2527712
sending data

问题

为什么会引发[Errno 202] EAI_FAIL异常？

谢谢!

Answer 1

看起来它与DNS有关，如在论坛帖子中所述的在这个答案中：

EAI_FAIL与无法解析DNS有关。

它看起来像是根植于getaddrinfo()函数(另一篇论坛帖子)中的特定于Pycom的错误代码。您还会发现在LTE博士中简短地提到了这个问题(请直说到"Pycom“部分)。

我猜这是在你设置client.base_url时调用的？我不认识你从Pycom文档里进口的一些东西。