Hi I'm working on server/Client project with C# that uses both TCP (for logging in and other stuff) and UDP (for streaming voice ). The problem is that I need to use sslStream for UDP but as far as I know its not possible to make SSL authentication with unguaranteed protocol. So is there anyway to make the authentication using TCP then use the sslStream for UDP?
Not knowing much about C# and sslStream, but: UDP is a datagram protocol and it does not guarantee that packet delivery, order and even can cause duplicate delivery. TCP instead is a stream protocol which guaranteed delivery etc. TLS works only on top of a protocol like TCP and not on top of UDP.
For UDP you would need to use DTLS instead. According to Wikipedia the Microsoft TLS Stack SChannel support DTLS 1.0 since Windows 7 and Windows 2008 R2. But when searching for C# DTLS lots of questions show up but nothing which would indicate that there is native support for DTLS with C#. But some third party libraries show up in this search which might help with your problem.