I'm searching for a sipphone program that can connect to many providers simultaneously and handle different sip providers. This way, if someone contacts any of my accounts, it will ring regardless of whatever provider is currently set up for outgoing calls.

Phonerlite can manage several accounts, as far as I can tell, but it just rings for the active account.

According to Zoiper, the free version is not portable.

Are there any suggestions for a free portable sipphone?