Host Connect Emulator uses TN3270 telnet and not the RSE server
to connect to the host.
When using secure telnet (encrypted communication) and
you are working with certificates that are not signed by a well-known
CA, every client must add the CA certificate to their Host Connect
Emulator list of trusted CAs.
The NOSNAEXT option of TCP/IP’s TELNETPARMS might
be necessary to disable the SNA functional extensions. If NOSNAEXT is
specified, the TN3270 telnet server does not negotiate for contention
resolution and SNA sense functions.