IMHO the truth of the matter is Client Access emulator requires a license from IBM to use. I believe it is checking for a license to connect to the host. While you do not need a license to connect to the telnet server. (Once you sign on you need a license for an interactive session.)
Just try to connect with our laptop to a company that did not purchase the client access licenses. MochaSoft licenses you at install and IBM make sure the server you are connecting to has a license to support your connection.
Director of Information Services
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of midrange
Sent: Sunday, August 09, 2015 12:59 PM
To: 'Midrange Systems Technical Discussion'
Subject: RE: Mocha TN5250 connects but not Client Access
Welcome to fat client versus thin client, an argument that is decades old.
The extra features in CA are the result of customers requesting the
Btw-fewer ports used (by itself) does not = better security.
CA gives admins the tools to secure various features and what the user sees.
Mocha fills a need for some customers as well.
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of
Sent: Sunday, August 09, 2015 11:30 AM
To: Midrange Systems Technical Discussion
Subject: Re: Mocha TN5250 connects but not Client Access
On Sun, Aug 9, 2015 at 10:54 AM midrange <franz9000@xxxxxxxxx> wrote:
As usual, ibm constantly changing the website makes it difficult to
find the list of ports Required - here is a 2014 version
I will guarantee Mocha does not have same requirements
I don't understand why Client Access would need any ports besides the telnet
port to give you a greenscreen session. I get that client access is a lot
more than an implementation of the telnet 5250 protocol, while mochasoft,
tn5250, tn5250j, x5250, etc are just greenscreen (and maybe
printer) clients. However, if I was a network admin in a situation where I
had to give an office/factory/warehouse full of people greenscreen access to
some RPG app that didn't have a web front end, I'm not going to want any
subnets besides the ones IT uses to connect to have access to all that extra
functionality. Principle of least privilege. That basically means that I'm
going to prefer a third party 5250 client for security purposes.