Q: If Rmpi runs well under a single PC but hangs if two or more PCs are used, what is the problem?
A: It is mostly likely caused by the firewalls on remote PCs. To confirm this, either turn off firewalls or launch Remote Desktop and Task Manger to see if Rterm.exe shows up. If remote PCs have Rterm.exe but Rmpi hangs, it's the firewall.