[Freeswitch-users] simple point to point voip (ATA) connection?

Hi, I have two ATAs - similar to Grandstream 488s, which allows me to convert analogue phones into IP streams. The config server for these devices has options for SIP and NAT/ STUN settings. Can anyone assist me in what I need to do to create a simple point-to-point call, essentially by entering IP addresses manually? The ultimate purpose is so that I can tunnel such connection through ssh tunnel/ forwarded ports. But the first step is to make the (point to point) connection. My machine is Ubuntu. Do I need a SIP server? If so, how can I ensure the RTP stream goes through an ssl forwarded port - ie, how do I ensure the RTP stream goes to a local port, which I then forward using ssh? Thanks in advance Zen