can't use socket and cryptography in unity by windows store

Hello,when I change my project to windows store platform,I find socket and cryptography can’t be used in windows store,So I want to use other class to replace these,and change net framework 3.5 to windows 8.1,hope give me some ideas ,thank you!!!

See:

for a list of all the .net classes that are supported on a Windows Store App app. When building for WSA Unity uses the MS provided .Net and not Mono. If Windows Store Apps do not have access to System.Net.Sockets that’s because MS doesn’t want you to use that feature.