Cyrus "hanging" when connecting to POP3 port several times

[Tomasz Chmielewski]

My Cyrus is hanging when I try to connect to the POP3 or POP3S port 
several times, i.e. when connecting like this three-four-five times in a 
row:

$ telnet 127.0.0.1 110
Trying 127.0.0.1...
Connected to localhost (127.0.0.1).
Escape character is '^]'.
+OK <2041089544.1231155840 at imap> imap1 Cyrus POP3 v2.3.13 server ready
quit
+OK
Connection closed by foreign host.

$ telnet 127.0.0.1 110
Trying 127.0.0.1...
Connected to localhost (127.0.0.1).
Escape character is '^]'.
+OK <2300500967.1231155842 at imap> imap1 Cyrus POP3 v2.3.13 server ready
quit
+OK
Connection closed by foreign host.

$ telnet 127.0.0.1 110
Trying 127.0.0.1...
Connected to localhost (127.0.0.1).
Escape character is '^]'.
+OK <2951207308.1231155844 at imap> imap1 Cyrus POP3 v2.3.13 server ready
quit
+OK
Connection closed by foreign host.

$ telnet 127.0.0.1 110
Trying 127.0.0.1...
Connected to localhost (127.0.0.1).
Escape character is '^]'.


And it waits like that for 10, 20, 30 seconds, until I get a reply, or 
just indefinitely, and I don't get any reply and connection times out.
In the meantime, I can open yet another connection from another 
terminal. Or not, because it will hang similarly.


The phenomenon does not happen for IMAP connections.


I tried Cyrus versions 2.3.11, 2.3.12 and 2.3.13 with different settings 
on different machines and I could reproduce this issue everywhere.
There is no firewall limiting the number of connections.

Is it a known problem? If yes, are there any workarounds to that? If no, 
what more information should I provide to help fix it?


-- 
Tomasz Chmielewski
http://wpkg.org