In software defined networking a controller can control where the data-plane routes packets to. Programmable data-planes make networks even more flexible, as the algorithms on the data-plane can be updated. The P4 programming language can be used to program data-planes, and the P4Runtime data-plane API can be used for controller to data-plane communication. The possibility of man-in-the-middle attacks when using P4Runtime was investigated. Man-in-the-middle attacks are possible either between the controller and data-plane, or between two hosts on the network. A virtual network in Mininet was used to try and demonstrate the difference between secure and insecure channels in these two scenarios. A malicious controller can take control of a switch in order to use it for man-in-the-middle attacks when the P4Runtime channel is insecure, but not in a secure channel. The man-in-the-middle attack between the controller and switch was not achieved due to the switches in Mininet only running on localhost and not being able to run the controller in-band. It was concluded that it is indeed recommended to only use secure P4Runtime channels, and possible extensions to this research could be to attempt the same experiment using a different setup or to research the effects that a successful man-in-the-middle attack can have.