Best practice for communication between 3 application

I have 3 applications which work together. On localhost only.

Application 1 and Application 2 are required and work together.

Application 3 is optional and when used, it work with Application 2.

Actually i have this design

App1(c#) <=== socket ===> App2(java) <=== socket ===> App3(c#)

Actually, App1 and 3 don't have to communicate, but that will change, but App3 still remain optional.

What is the best practice ? Keep my socket, and transfer from App1 to App3 through App2 ? Or create one new socket directly between App1 and App3, so more thread, and maybe less quickly.

Knowing that App2 and 3 use already a lot of CPU.