We finally got it ready – 3CX Phone System V5.1. A lot of hard work of the 3CX team went into that one, and I think it shows. We have made numerous improvements and fixes, and introduced the much awaited 3CX Tunnel feature. The 3CX Tunnel allows for remote extensions and branch offices to be connected via a single TCP port.
You no longer need to open a range of ports for RDP and SIP traffic but you can tunnel it all over a single, configurable port. That means you can use port 80 (if you are not using a web server in your office location) and be sure that remote extensions can connect from anywhere, even if they are in hotel or airport wifi networks which sometimes block higher ports in order to block VOIP traffic .
The 3CX tunnels regular SIP traffic, which means that you can use popular SIP hardware phones as remote extensions. They simply use the 3CX tunnel as an outbound proxy. See a configuration guide here. This in contrast to other tunneling protocols such as IAX which require the remote party to implement the IAX protocol and thus limit the devices/software that you can use. Download 3CX Phone System V5.1 here.