TN3270, or Telnet 3270, is a form of Telnet service that enables access to mainframe hosts over a TCP/IP network. By using Microsoft SNA Server, users running a TN3270 client can connect to mainframe computers using the TN3270 service included with SNA Server.
TN3270 (Telnet 3270) was developed as an alternate to the regular Telnet service for accessing mainframe computers.
TN3270 provides a better look and feel than standard Telnet, but its numeric field handling and keyboard interface are somewhat clumsy.
TN3270 provides keyboard emulation and block-mode service at the client level, thus freeing the mainframe from translation functions. TN3270 provides workstation emulation only and does not include file-transfer or printer-emulation services.
You can also use TN3270 to connect to AS/400 systems, but the AS/400 systems must translate the 3270 data stream into 5250 format and provide keyboard mapping between the 3270 and 5250 key sequences, a process that consumes additional CPU resources on the AS/400.