Hello, A '2' is suffixed to the socket ip number of gmsh: for instance, configured with "localhost:10000" (through the GUI or the Gmsh Option File) gmsh will in fact listen to the port 10002. I could not find information regarding this behavior in the documentation so I suspect it is a bug. I observed the phenomenon with gmsh 2.6.2 and 2.8.2. With kind regards, Pierre