Python 尝试/排除 SMTPLib 问题

Question

我使用 Python 的 SMTPLib 编写了一个简单的 SMTP 客户端。只是尝试添加一些错误处理 - 特别是在这种情况下，当要连接的目标服务器不可用时（例如，指定了错误的 IP！）

目前，回溯如下所示：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "smtplib_client.py", line 91, in runClient
    try:
  File "/usr/local/lib/python2.7/smtplib.py", line 251, in __init__
    (code, msg) = self.connect(host, port)
  File "/usr/local/lib/python2.7/smtplib.py", line 311, in connect
    self.sock = self._get_socket(host, port, self.timeout)
  File "/usr/local/lib/python2.7/smtplib.py", line 286, in _get_socket
    return socket.create_connection((host, port), timeout)
  File "/usr/local/lib/python2.7/socket.py", line 571, in create_connection
    raise err
socket.error: [Errno 111] Connection refused

很明显，socket.py 中的“create_connection”正在爆炸。这有它自己的 try / except 块：

for res in getaddrinfo(host, port, 0, SOCK_STREAM):
    af, socktype, proto, canonname, sa = res
    sock = None
    try:
      sock = socket(af, socktype, proto)
      if timeout is not _GLOBAL_DEFAULT_TIMEOUT:
          sock.settimeout(timeout)
      if source_address:
          sock.bind(source_address)
      sock.connect(sa)
      return sock

    except error as _:
      err = _
      if sock is not None:
          sock.close()

if err is not None:
  raise err
else:
  raise error("getaddrinfo returns an empty list")

我的 runClient() 函数如下所示：

def runClient(configName = 'default', testFile = './test.xml'):
  cliCfg = getClientConfig(configName)
  print cliCfg.find('logfile').text
  # startLogger(cliCfg.find('logfile').text)
  clientCert = cliCfg.find('cert').text
  clientKey = cliCfg.find('key').text
  serverHost = cliCfg.find('serverhost').text
  serverPort = int(cliCfg.find('serverport').text)

  myMail = MailMessageHandler()
  msgSrc = myMail.readMessageSource(testFile)
  allMsgs = myMail.processMessages(msgSrc)
  inx = 1
  for msg in allMsgs:
    validMsg = True
    requiredKeys = ('ehlo', 'sndr', 'rcpt', 'body')
    for msgItems in requiredKeys:
      if len(msg[msgItems]) == 0:
        validMsg = False
    if validMsg:
      try:
        server = smtplib.SMTP(serverHost, serverPort)
        server.ehlo(msg['ehlo'])
        thisSender = msg['sndr']
        thisRecipient = msg['rcpt']
        thisMessage = MIMEText(msg['body'])
        thisMessage['To'] = email.utils.formataddr(('', thisRecipient))
        thisMessage['From'] = email.utils.formataddr(('', thisSender))
        thisMessage['Subject'] = msg['subject']
        thisMessage['Message-id'] = email.utils.make_msgid()
        now = datetime.now()
        day = now.strftime('%a')
        date = now.strftime('%d %b %Y %X')
        thisMessage['Date'] = day + ', ' + date + ' -0000'
        if msg['tls'].lower() == 'true':
          server.starttls('certs/client/client.key', 'certs/client/client.crt')
          logging.info ("Message: " + thisMessage['Message-id'] + " to be sent over TLS")
        server.sendmail(thisSender, thisRecipient.split(","), thisMessage.as_string())
        logging.info ("Message: " + thisMessage['Message-id'] + " sent successfully to " + serverHost + ":" + cliCfg.find('serverport').text)
        logging.info ("Message: " + thisMessage['Message-id'] + " had sender: " + thisMessage['From'])
        logging.info ("Message: " + thisMessage['Message-id'] + " had recipient(s): " + thisMessage['To'])
      except socket.error as e:
        print "Could not connect to server - is it down? ({0}): {1}".format(e.strerrror)
      except:
        print "Unknown error:", sys.exc_info()[0]
      finally:
          server.quit()
    else:
      print "Improperly formatted source mail - please check"

我不明白的是 - 回溯显示了对raise err. 显然err不是 None，因此必须将其设置为except error as _:...的一部分。因此，错误最初被处理，但作为处理程序的一部分，创建了一个副本 ( err) - 随后在 try/ except 之外引发块 - 所以未处理。然后，这个未处理的错误应该“传递回”调用堆栈（get_socket没有 try/ except 块，也没有connect或__init__- 所以在原始errorin的 try/ except 块之外create_connection，错误的副本，err肯定应该“级联” “回到 runClient 函数中的 try/ except 块？

Answer 1

在 @AndreySobolev 的支持下，我得到了以下简单的代码，运行良好：

import smtplib, socket

try:
   mylib = smtplib.SMTP("127.0.0.1", 25)
except socket.error as e:
   print "could not connect"

所以我然后返回到我的 smtplib_client.py，并块注释掉了大部分“尝试”部分。这工作得很好......所以一点一点地，我恢复了越来越多的尝试部分......并且每次都工作得很好。最终版本如下。除了我在处理程序中所做的之外except socket.error，我不能说我知道我所做的任何更改 - 除了我还添加了一个server = None以停止finally部分工作之外。哦，我还必须将“socket”添加到我的导入列表中。如果没有这个，我可以理解 except 不能正确处理 - 但我不明白为什么它根本没有触发，甚至生成“未定义”错误......奇怪！

工作代码：

def runClient(configName = 'default', testFile = './test.xml'):
  cliCfg = getClientConfig(configName)
  print cliCfg.find('logfile').text
  # startLogger(cliCfg.find('logfile').text)
  clientCert = cliCfg.find('cert').text
  clientKey = cliCfg.find('key').text
  serverHost = cliCfg.find('serverhost').text
  serverPort = int(cliCfg.find('serverport').text)

  myMail = MailMessageHandler()
  msgSrc = myMail.readMessageSource(testFile)
  allMsgs = myMail.processMessages(msgSrc)
  inx = 1
  for msg in allMsgs:
    validMsg = True
    requiredKeys = ('ehlo', 'sndr', 'rcpt', 'body')
    for msgItems in requiredKeys:
      if len(msg[msgItems]) == 0:
        validMsg = False
    if validMsg:
      try:
        server = None
        server = smtplib.SMTP(serverHost, serverPort)
        server.ehlo(msg['ehlo'])
        thisSender = msg['sndr']
        thisRecipient = msg['rcpt']
        thisMessage = MIMEText(msg['body'])
        thisMessage['To'] = email.utils.formataddr(('', thisRecipient))
        thisMessage['From'] = email.utils.formataddr(('', thisSender))
        thisMessage['Subject'] = msg['subject']
        thisMessage['Message-id'] = email.utils.make_msgid()
        now = datetime.now()
        day = now.strftime('%a')
        date = now.strftime('%d %b %Y %X')
        thisMessage['Date'] = day + ', ' + date + ' -0000'
        if msg['tls'].lower() == 'true':
          server.starttls('certs/client/client.key', 'certs/client/client.crt')
          logging.info ("Message: " + thisMessage['Message-id'] + " to be sent over TLS")
        server.sendmail(thisSender, thisRecipient.split(","), thisMessage.as_string())
        logging.info ("Message: " + thisMessage['Message-id'] + " sent successfully to " + serverHost + ":" + cliCfg.find('serverport').text)
        logging.info ("Message: " + thisMessage['Message-id'] + " had sender: " + thisMessage['From'])
        logging.info ("Message: " + thisMessage['Message-id'] + " had recipient(s): " + thisMessage['To'])
      except socket.error as e:
        logging.error ("Could not connect to " + serverHost + ":" + cliCfg.find('serverport').text + " - is it listening / up?")
      except:
        print "Unknown error:", sys.exc_info()[0]
      finally:
        if server != None:
          server.quit()
    else:
      print "Improperly formatted source mail - please check"

困惑之余，又释然了！谢谢安德烈！