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TCP/TELNET virtual service requires a challenge response before the first request

Question asked by JasonArmitage on Feb 12, 2016
Latest reply on May 23, 2017 by pbernard.1

I'm trying to virtualize a legacy mainframe service that communicates with TELNET over TCP.  This service requires the server to send a challenge/handshaking response as soon as the TCP session is established, before the client has sent a request.


The problem I'm facing is that when using a standard model; the TCP session is started and the TCP listener node sits waiting for the client to send a request, and the client sits waiting for the server to send a challenge/prompt first.


I have tried adding a script task before the TCP listener to handle this initial handshaking conversation, but unless I close the TCP session in the script the following TCP listener fails with a "port in use" error. The TCIP/IP Listener can't use the session the script has started, and if the session is dropped then the handshaking needs to be done again.