B3270 opens a telnet connection to an IBM host, handling the 3270, TELNET and TLS protocols, allowing a front-end application handle user interactions. It uses XML on its standard input and standard output to communicate with the front end.

b3270 implements RFCs 2355 (TN3270E), 1576 (TN3270) and 1646 (LU name selection), and supports IND$FILE file transfer.