[arch-general] failed retrieving file 'core.db' in "pacman -Syu"

[mudongliang]

# pacman -Syu
:: Synchronizing package databases...
error: failed retrieving file 'core.db' from mirrors.ustc.edu.cn : Recv failure: Connection reset by peer
error: failed retrieving file 'core.db' from mirrors.163.com : Recv failure: Connection reset by peer
error: failed retrieving file 'core.db' from archlinux.polymorf.fr : Recv failure: Connection reset by peer
error: failed retrieving file 'core.db' from fooo.biz : Recv failure: Connection reset by peer
error: failed retrieving file 'core.db' from mirror.one.com : Recv failure: Connection reset by peer
^C
Interrupt signal received

But I found that I can ping mirrors.ustc.edu.cn
# ping mirrors.ustc.edu.cn
PING mirrors.ustc.edu.cn (202.38.95.110) 56(84) bytes of data.
64 bytes from mirrors.ustc.edu.cn (202.38.95.110): icmp_seq=1 ttl=128 time=5.46 ms
64 bytes from mirrors.ustc.edu.cn (202.38.95.110): icmp_seq=2 ttl=128 time=5.68 ms
64 bytes from mirrors.ustc.edu.cn (202.38.95.110): icmp_seq=3 ttl=128 time=5.07 ms
^C
--- mirrors.ustc.edu.cn ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 5.076/5.410/5.686/0.252 ms

I don't know what's the problem about my x86_64 archlinux. 

-- 
My best regards to you.

     No System Is Safe!
     mudongliang