listener-thread: err = -25582: oserr = 0: errstr = : Network connection is broken

Hello everybody!
I need your help!
There was an error("17:08:04 listener-thread: err = -25582: oserr = 0: errstr = : Network connection is broken." or "20:18:04 listener-thread: err = -25580: oserr = 4: errstr = : System error occurred in network function. System error = 4.") in the online.log.The error bothering me, but I don't know what it is hidden danger.

It doesn't happen very often and there is no law.Seen as follows：
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Sun Sep 8 00:01:19 2013
16:48:04 listener-thread: err = -25582: oserr = 0: errstr = : Network connection is broken.
……
Tue Sep 10 00:00:50 2013
06:28:04 listener-thread: err = -25580: oserr = 4: errstr = : System error occurred in network function.System error = 4.
……
Wed Sep 11 00:00:40 2013
19:28:14 listener-thread: err = -25582: oserr = 0: errstr = : Network connection is broken.
……
Mon Sep 16 00:00:16 2013
08:08:04 listener-thread: err = -25582: oserr = 0: errstr = : Network connection is broken.
……
Fri Sep 20 00:00:30 2013
22:18:04 listener-thread: err = -25582: oserr = 0: errstr = : Network connection is broken.
……
Sat Sep 21 00:00:23 2013
14:58:04 listener-thread: err = -25582: oserr = 0: errstr = : Network connection is broken.
……
Mon Sep 23 00:00:41 2013
03:48:04 listener-thread: err = -25580: oserr = 4: errstr = : System error occurred in network function.System error = 4.
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What is the effect of this problem and hidden trouble, how should I handle？