Marty's WiFi interface needs a couple of ports to be open between Marty and your computer to be able to communicate properly.
You may need to ask for an IT manager or computing support person to help with this if you're in a school or have managed WiFi. If you're at home, these ports are usually open by default, so you don't need to change anything.
Marty uses the following ports:
80for the web-based alternative calibration tool
23for un-managed TCP sockets (used by Python)
24for managed TCP sockets (also Python)
4000for UDB broadcasts, used to scan for Martys in some cases (Python, Scratch)
You'll also need to check that the firewall on your computer itself (if you have one configured) is also not blocking this traffic.
A computer and a Marty also need to be able to internally communicate within a network, so depending on the router and firewall configuration, traffic between a Guest network and your main network may need to be explicitly allowed, as this is commonly disabled. Bare in mind the security implications this may have - don't edit firewall configurations if you don't fully understand what the configuration changes you are making will do!
Additionally, we recommend that the Martys and the computers communicating with them are on the same subnet. This generally ensures that the Marty scanners will be able to find your Marty.
If you need to add rules allowing traffic for specific MAC addresses only, see our other article on How to find Marty's MAC address