SIMH revamp episode #2

OK, so a confession – I may have contributed to my SIMH VAX emulator DECnet connectivity issues. At various times I’ve had the bridge software (that squirts TCP/IP UDP packets containing DECnet data too and forth between DECnet area routers) running on a Raspberry PI. The Kingston SD CARD I had in the PI started exhibiting weird errors so I ordered another one pre-installed with noobs.  SD CARDS seem to vary enormously in quality, speed and reliability so I thought I’d just spend a couple more quid and get one that was recommended.

So last night I compiled up the bridge software on the Raspberry PI, went to configure my ADSL router to change routing of UDP packets on port 4711 to the PI rather than the HP Microserver that was causing all the grief only to find that the NAT configuration was already pointing to the PI! This would have caused no end of grief – and could have been the root cause of my problems. Anyway, I thought I persevere with this option as I’d also found other issues with the HP Microserver networking and am now happy to report that connectivity issues appear resolved.

The SIMH VAX instance on the HP Microserver appears on hecnet as SIMVAX (node address 4.248). Success means an area list like this:

This is now reflected on the internet at

Showing the circuit give a list of the adjacent router nodes:

I can now do fun things like jumping on other machines in the network, including simulated and real PDP, VAX, Alpha and Itanium boxes, for example:

This may be somewhat unrelated to my Retrochallenge goals but I was really quite sick of this issue and thought I’d just persevere under the auspices of Retrochallenge until I was happy this was all now working.

Onwards and upwards…