New submission from Joel Hillacre:
I am encountering a ResourceWarning about an unclosed socket when getting a non
220 response during connect() in __init__() of smtplib.SMTP. Attached are a
client script causing this warning for me, a server script to cause the client
to the warning and a patch that fixes the warning for me. My python version is
Python 3.6.1 (default, Apr 7 2017, 09:32:32) [GCC 4.8.5 20150623 (Red Hat
4.8.5-11)] on linux. I had found previous related issue with similar symptom
and remedy in issue #21641.
$ python3.6 test_server.py
connected by ('127.0.0.1', 53630)
$
$ python3.6 test_client.py
Traceback (most recent call last):
File "test_client.py", line 2, in <module>
smtp = smtplib.SMTP('127.0.0.1', 8025)
File "/usr/lib64/python3.6/smtplib.py", line 253, in __init__
raise SMTPConnectError(code, msg)
smtplib.SMTPConnectError: (554, b'Nope.')
/usr/lib64/python3.6/socket.py:657: ResourceWarning: unclosed <socket.socket
fd=4, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6,
laddr=('127.0.0.1', 53630), raddr=('127.0.0.1', 8025)>
$
RFC 2821 states that servers responding with non 220 greetings must not close
the connection. It is this behaviour that test_server.py is using to trigger
the warning in test_client.py.
RFC 2821 Section 3.1 Paragraph 3
https://tools.ietf.org/html/rfc2821#section-3.1
'... a 554 response MAY be given in the initial connection opening message
instead of the 220. A server taking this approach MUST still wait
for the client to send a QUIT (see section 4.1.1.10) before closing
the connection and SHOULD respond to any intervening commands with
"503 bad sequence of commands".'
The ResourceWarning is no longer caused for me after applying this change.
----------
components: Library (Lib)
files: smtplib.patch
keywords: patch
messages: 293905
nosy: jhillacre
priority: normal
severity: normal
status: open
title: smtplib leaves open sockets around if SMTPConnectError is raised in
__init__
type: enhancement
versions: Python 3.6
Added file: http://bugs.python.org/file46873/smtplib.patch
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