AS400 session reset ??

I'm just an application programmer and don't know
much about AS400 but here goes:

I am told if our client goes down a session can be left connected
on AS400 so when client comes back up it can't connect.

I'm told I should be able to figure out from tn5250 code, which source
ports are probably in use.  I've perused the source and can't find this code.

Then I am told, because this kludge was apparently done on a previous client we
had:
I can send a tcp syn/reject  dport=23 sport=?? to the As400 from the client
and it will disconnect the old session.

Is the above true?
Can anyone help me implement this or point me to sample code which looks like
above?
Or better yet, is there something which will cause tn5250 to do these resets
upon initialization.?
Or better yet, can I patch the code to do this reset before each connect
attempt.?
Or better yet, its already being done and my people are full of crap?