TU Darmstadt's WiFi network on campus is provided by HRZ. It offers Internet access and can be used free of charge with a valid TU-ID, guest ID, or as a partner in eduroam/DFN roaming. The according pages about this WiFi contain various installation instructions and information on the technology used.
Network access in public areas, such as ULB, and lecture halls can also be provided via IEEE 802.1X sockets with network cables. The number of public network sockets for Internet access is constantly increasing.
VPN access allows you to use TU Darmstadt's WiFi off campus as well, for example at the university's library. You can find the installation instructions on the websites about VPN.