36 lines
1.8 KiB
Plaintext
36 lines
1.8 KiB
Plaintext
MBOX-Line: From drescher at pro-image.de Mon Sep 18 00:07:10 2006
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To: imap-protocol@u.washington.edu
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From: Christof Drescher <drescher@pro-image.de>
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Date: Fri Jun 8 12:34:37 2018
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Subject: [Imap-protocol] Avoiding connection-loss
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Message-ID: <009901c6daf1$1026f580$2d65a8c0@ProImage.local>
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Hi,
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I recently got a report from a user connecting to our imap server about an IDLE-connection dropping with an error message. Client was Outlook Express which showed an error like "lost connection to imap server". After some investigation I found the reason in a modern AVM FritzBox NAT router, which seems to close inactive connections after about 15 minutes.
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Now, as IMAP-IDLE allows for about 30 minutes inactivity by design, this behavior of the NAT router is not nice at all, and as I could not change this behavior by any setting on the router, I was rather stuck.
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So, I changed the server-implementation of the IDLE command like the following: If the user is IDLE for more than 290secs (near to 5 minutes, the least I could imagine for a NAT router dropping a connection), I repeat the last EXISTS to keep the connection open. E.g.
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[C] abrr SELECT "INBOX"
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[S] * 1 EXISTS
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[S] * 0 RECENT
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[S] [...]
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[S] abrr OK [READ-WRITE] SELECT completed
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[C] brum IDLE
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[S] + idling
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[S] * 2 EXISTS // new message arrives
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[S] * 1 RECENT // new message arrives (2)
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[S] * 2 EXISTS // 290secs inactivity
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[S] * 2 EXISTS // another 290secs inactivity
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[C] DONE
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[S] brum OK IDLE terminated
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Now - is this protocol compliant (I think yes). Is there any scenario where this may confuse clients? Any other problem imaginable?
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Christof
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