Firewall filters and inspection

Some service providers block the default port 1194 (both TCP and UDP) from some client networks. Corporate networks, as an easy example, block most inbound traffic to the network, preventing a rogue service like a web server or OpenVPN server. On a much larger scale, one infamous blockade for the OpenVPN service is the Great Firewall of China (see https://openvpn.net/archive/openvpn-devel/2004-11/msg00028.html for more information).