Mainframe - Handshake Error Displayed When Connecting
This web article deals with an error when connecting to the mainframe. The error may contain the words "unable to connect" or "handshaking". The solution is to go though the configuration settings and update as necessary.
If you are attempting to login to the mainframe and getting an error message including "unable to connect" or "handshaking", then the configuration settings of your client may need updating. You should compare the settings in your client with the ones in the mainframe configuration document (Mainframe - Installing and configuring QWS3270 Secure for Windows), especially the settings in the two Security screenshots. Make the updates as necessary. This should allow you to connect successfully.