From The x3270 Wiki

b3270 is a generic back end for 3270 emulators. b3270 implements the 3270 protocol and host input/output, and communicates with a front end application (the thing that actually draws the image of the terminal display on the screen and captures keystrokes) using a simple XML- or JSON-based protocol. It is currently used by wx3270.

b3270 example

See also

b3270 protocol

Release Notes