Hi Roger,
No, that port is open on the server.
In the meantime I did some more tests: I ran a new install, using the new storage service obviously, but I got the same error. Then I ran a new install on another machine, again exactly following the manual instructions, but also with the same result.
Finally I ran a new install on those machines following the manual instructions for the v1.12.x Archivematica version and that worked like a charm (as before). So I suspect there is something wrong or missing in the manual instructions for the v1.13.x Archivematica version and I know the Archivematica team is used to copy/paste a lot when coming up with new version documentation, so this wouldn't surprise me.
Best regards,
Vin