My protocol analyser for the TN3270 protocol is now available in Wireshark. TN3270 is the protocol created by IBM in 1972 for a class of terminals normally used to communicate with IBM mainframes. There was a time when TN3270 accounted for a significant portion of the world’s network traffic and it is still widely used today – mainly because big iron just refuses to lie down and die. The omission from Wireshark of such an important protocol in the history of network communications always struck me as a little odd. So with the help of the trusty “3270 Information Display System: Data Stream Programmer’s Reference” (all 500 or so pages of it) I set to work. It rapidly became an exercise in typing, rather than coding. And the only reason I finished it was because I started it. Next up – TN5250.