The default version of shellinabox doesn’t seem to be working on 12.3. When I try to access https://localhost:4200 I am seeing certificate errors on the browser. The problem has been fixed in version 2.11, but 12.3 only has 2.10 available from the standard repository.
I found this RPM: ftp://rpmfind.net/linux/opensuse/factory/repo/oss/suse/x86_64/shellinabox-2.14-4.6.x86_64.rpm
which can be installed on 12.3 to address this issue. Unfortunately this version does not work on SLES 11.2/3 as it required openssl 1.0.0 which is not present in 11.2/3.