Hi,
My friend and I have been trying to achieve this for a few weeks now.
We have tried Skype Audio, Jammr, and Jamkazam without success. All free programs by the way. One can play while the other listens without a problem. When we both play at the same time one of us drops out.
These programs, except Skype, have very poor instruction. They really need a step by step, that clearly illustrates the process.
I should say that my friend is very, very, digitally challenged, and I have been instructing him remotely. Therefore I cannot have confidence he was setting up his side properly.
I wouldn't mind paying a small amount monthly in order to do this. But I have not found any other providers but for what I have listed. We stopped trying as it was becoming too frustrating for us trying to set it up.
If I find anything interesting, I will post.
John