Cannot install Plesk license key: cURL cannot communicate with license server

[sachinj]

How to fix cURL cannot communicate with license server?
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License installation fails with one of the following errors:

Error: cURL cannot communicate with license server https://id-00.kaid.plesk.com:5224/ (): Couldn't connect to server(7)
cURL cannot communicate with license server https://id-00.kaid.plesk.com:5224/ (): Couldn't resolve host name(6)

Error: No properly formed ip addresses

Error: The license key is invalid. In order to use Plesk, you need to obtain and install a new valid license key. Your license key has expired. To continue using your Plesk, you must purchase a non-expiring commercial license key. Error: cURL cannot communicate with license server https://id-00.kaid.swsoft.com:5224/ (): Failed to connect to id-00.kaid.swsoft.com port 5224: Bad access(7) cURL cannot communicate with license server https://id-00.kaid.swsoft.com:5224/ (): Could not resolve host: id-00.kaid.swsoft.com(6)

ERR [panel] KeyUpdate Result additional information: cURL verbose output: * Trying 195.214.233.80... * connect to 195.214.233.80 port 5224 failed: Bad access * Failed to connect to ka.plesk.com port 5224: Bad access * Closing connection 0

Cannot telnet to ka.plesk.com:

Code: [Select]

# telnet ka.plesk.com 5224
Trying 195.214.233.80...
telnet: Unable to connect to remote host: Connection refused
Cause
========

Firewall on a server is blocking the connection to Plesk licensing server ka.plesk.com.

Since February 5, 2018, ka.plesk.com (KA, Key Administrator, a Plesk licensing server) hostname resolves to 3 different IP addresses based on round-robin:

    195.214.233.80 (old one)
    195.214.233.81 (new)
    195.214.233.82 (new)

Additionally, since the same day KA accepts connections from Plesk on two ports:

    5224 (old one, non-standard port)
    443 (new, the default HTTPS port)

Plesk server should be able to establish connection to all three KA IP addresses and both KA ports in all their combinations (see the table below):
IP    Port
195.214.233.80     5224
195.214.233.80     443
195.214.233.81     5224
195.214.233.81     443
195.214.233.82     5224
195.214.233.82     443

Resolution
==========

Allow connection using SSH connection:

   > Log in to the server over SSH
   >  Add the following rules to the local firewall. For example, iptables:

Code: [Select]

# iptables -I OUTPUT -p tcp -d 195.214.233.80,195.214.233.81,195.214.233.82  -m multiport --dports 443,5224 -j ACCEPT
# iptables -I INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

Check the Key Administration server connectivity:

Code: [Select]

# telnet ka.plesk.com 5224
# telnet ka.plesk.com 443
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Cheers!