Sometimes, a firewall does not permit to set up a SIP phone call. So overcomes such problems, Sipcast.Net service incldues a VPN server.
For example, if your in a hotel or the SIP connection does not work anymore, start the OpenVPN program and establish a connection. Then, all data will transmitted via a VPN tunnel to the Sipcast server which out being harms by a firewall.
In addition, if the Internet connect is bad, you can try to use the VPN connection, too. Then, all data will be transmitted loss less albeit at a higher delay.
Our OpenVPN service uses TCP and TLS via the port 443.