How to communicate between 2 programs efficiently?

What is an easy to implement way to communicate between 2 vb.net (3.5) form applications that are running on the same machine?

The current problem is that in each program a user needs to be logged into to use. If the user is logged into one, and clicks a button to launch another, it should pass who is logged in so they do not need to log in again in the second program.

I am looking for a solution that can be used for oth开发者_开发问答er purposes as well.

Note: I am not a VB.NET developer myself, a member of the team I am managing expressed difficulties with this task and I am trying to research a possible solution for him.

You can do use socket to pass information around. This solution will work for almost any two programs written in any language.

Binary Remoting can also work well for this if everything is .net based.