> When I specify hostname for host attribute, the connection is successful. However, when I specify the IP address, it fails. I guess it's some setting on the server itself
That's the way Synergy works. The name you specify as -host parameter is not a DNS name or IP address. It's simpy a string that is matched by the server (the object registrar to be precise) against the name of all knwon ESD instances. If you want to allow clients to use different names ("aliases"), add them in the file $CCM_HOME/etc/esd.adr on your server after the initial "host:port" pair, e.g.