Because it needs to use UDP. UDP packets are univesally banned by browsers to prevent internet pranks and DDOS. Many larger companies just toss all UDP on the ground like fascists, but because videogaming is becoming part of life, destroying UDP is less common than 10 years ago. UDP can lie about where it came from , because it is stateless. It also has a hard time knowing if the port its going to is for its own private use. UDP is very low level, but not so low level that its indivisable or non-tunnel-friendly. Here is the C (not C++) source code to Moonlight (also known as NVIDIA Shield Gamestreaming protocol) : https://github.com/irtimmer/moonlight-common-c NVIDIA Shield is now called Moonlight open source Gamestreaming protocol..... and its based on UDP set to 1024 bytes