Improve the check for ports which have gone missing, and just ignore them.  We want a run to perform as much work as possible before it gives up.
Improve the check for ports which have gone missing, and just ignore
them.  We want a run to perform as much work as possible before it
gives up.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase