a <host> running a telnet 3270 server to which connect to run experiment from a client
depending on Your needs and time available maybe the best way is to install on Your PC a TN3270 server
free to test at any time, even devising different 3270 screen situations
I would grab the hercules s/370-s/390-esame emulator and the turnkey mvs 3.8 distribution...
it is free it can run 3270 tso sessions ( even if old it is workable )
it should not take more than an afternoon to have it up and running
( I was abou to say a couple of hours, but I gave You a better chance )