This operation is only allowed using a successfully authenticated context

Question

I want to make client-server application with tcp encryption, but i have error when i try to send any message: This operation is only allowed using a successfully authenticated context. I already have: Certificate = new X509Certificate2("./server.pfx"); SslStream.AuthenticateAsServer(Certificate, false, false); in server and SslStream.AuthenticateAsClient("192.168.0.4"); in client.