$ sudo apt-get update
Err:1 http://kr.archive.ubuntu.com/ubuntu xenial InRelease
Could not connect to kr.archive.ubuntu.com:80 (103.22.220.133). - connect (111: Connection refused)
Err:2 http://kr.archive.ubuntu.com/ubuntu xenial-updates InRelease
Unable to connect to kr.archive.ubuntu.com:http:
Err:3 http://kr.archive.ubuntu.com/ubuntu xenial-backports InRelease
Unable to connect to kr.archive.ubuntu.com:http:
Err:4 http://kr.archive.ubuntu.com/ubuntu xenial-security InRelease
Unable to connect to kr.archive.ubuntu.com:http:
Hit:5 http://ppa.launchpad.net/i2p-maintainers/i2p/ubuntu xenial InRelease
Get:6 ftp://ftp.gajim.org/debian unstable InRelease [5,750 B]
Get:7 ftp://ftp.gajim.org/debian unstable/main amd64 Packages [2,208 B]
Get:8 ftp://ftp.gajim.org/debian unstable/main i386 Packages [2,207 B]
Get:9 ftp://ftp.gajim.org/debian unstable/main all Packages [2,206 B]
Fetched 12.4 kB in 9s (1,313 B/s)
Reading package lists... Done
W: Failed to fetch http://kr.archive.ubuntu.com/ubuntu/dists/xenial/InRelease  Could not connect to kr.archive.ubuntu.com:80 (103.22.220.133). - connect (111: Connection refused)
W: Failed to fetch http://kr.archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease  Unable to connect to kr.archive.ubuntu.com:http:
W: Failed to fetch http://kr.archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease  Unable to connect to kr.archive.ubuntu.com:http:
W: Failed to fetch http://kr.archive.ubuntu.com/ubuntu/dists/xenial-security/InRelease  Unable to connect to kr.archive.ubuntu.com:http:
W: Some index files failed to download. They have been ignored, or old ones used instead.