Well normally you need to configure with the CMOD server tool the "remote CMOD" instance.
So basically you launch "OnDemand Configurator", and then you create a new instance of CMOD, and then instead of creating a new instance on your workstation, you create a instance as a "remote" library server.
You give the hostname and the port, with a instance name... and then you can use the arsload -h with the name of the instance.
That's the "normal" way to do it, that way you can also create a SSL connection, if you ever need it.
With the solution "arsload -h hostname" you cannot do that.