What to do When Contact With License Server Fails?

When your server fails to contact the license server, it may be an easy fix on your end. Please check the following before you log a ticket.

Is your server DNS ok?

To check your DNS, run:

ping gooogle.com

Does it return the right result? (Don't try to ping our license server since it is not allowed.)

~> ping google.com
PING google.com ( 56(84) bytes of data.
64 bytes from lga25s63-in-f14.1e100.net ( icmp_seq=1 ttl=128 time=10.1 ms
64 bytes from lga25s63-in-f14.1e100.net ( icmp_seq=2 ttl=128 time=11.3 ms
64 bytes from lga25s63-in-f14.1e100.net ( icmp_seq=3 ttl=128 time=12.5 ms

Does telnet work?

If your DNS is ok, you can try to telnet to our license server by using port 443. Try license and/or license2.

telnet license.litespeedtech.com 443
telnet license2.litespeedtech.com 443
~> telnet license.litespeedtech.com 443
Connected to license.litespeedtech.com.
Escape character is '^]'.
telnet> quit 
Connection closed.

If you see the above, it means your server can connect to LiteSpeed's license server without any problem.

Does curl work?

Run the following curl commands:

curl -I -k https://license.litespeedtech.com
curl -I -k https://license2.litespeedtech.com
~> curl -I -k https://license.litespeedtech.com
HTTP/1.1 404 Not Found
Date: Tue, 05 Jun 2018 18:54:16 GMT
Accept-Ranges: bytes
Server: LiteSpeed
Alt-Svc: quic=":443"; ma=2592000; v="35,37,38,39"
Connection: Keep-Alive

If you see the above, it means your server connected to the license server without any problem. Don't worry about “404 Not Found”. It is normal.

Check your DNS server and Disable IPv6 DNS server

Check if there's any IPv6 DNS nameserver. Our license server does not like IPv6 mapped IPv4 addresses.

cat /etc/resolv.conf
nameserver 2620:0:ccc::2
nameserver 2620:0:ccd::2
nameserver 2001:4860:4860::8888

If so, comment out the IPv6 server records and try to verify license again.

#nameserver 2620:0:ccc::2
#nameserver 2620:0:ccd::2
#nameserver 2001:4860:4860::8888

Check your service provider

If your server can connect to the license server without any problem but it still returns “failed to contact license server”, most likely your datacenter blocks the license server. You will need to contact your service provider to fix it.

Add license server IPs to whitelist

If you would like to add our license server IPs to whitelist, you can add whatever the following resolved to:


At the time is writing, they are and, but they may be changed and you will need to check IPs yourself to make sure.

litespeed_wiki/licenses/failed-to-contact-license-server.txt · Last modified: 2019/01/08 18:44 by Jackson Zhang