Unfortunately FLDIGI, gives me the Hamlib error (when I tried it by itself), why trying it as "stand alone" ; well, I do need to be "present" for nets on Olivia Mode. Everything else "hand-shaked" as expected. Thanks
If MLDX is holding the port, Fldigi won't be able to access the port. It is one or the other. If you don't configure Fldigi to talk to MLDX via the UDP interface, then I would recommend you shutdown MLDX whenever you want to use Fldigi and look at using Flrig or the RigCAT option for the TS870.