When Linux cant run WHOIS and returns: "Unable to connect to remote host" it means firewall blocking port 43 (that port is not allowed in outgoing TCP ports).. i editted my config server firewall /etc/csf/csf.conf and restarted firewall by "csf -r" and WHOIS started working

# whois something.cz
[Querying whois.nic.cz]
[Unable to connect to remote host]

# whois yahoo.com
[Querying whois.verisign-grs.com]
[Unable to connect to remote host]
Another thing can be to try checking /etc/hosts or /etc/resolv.conf