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A3270 Emulator is aterminal emulator that duplicates the functions of anIBM 3270mainframe computer terminal on a computer, usually aPC or similarmicrocomputer.
As the original 3270 series terminals were connected to thehost computer through a display controller (cluster controller)[a] usingcoaxial cable, emulators originally required channel (rare), coax or synchronous communication adapter cards to be installed in the PC. Today, many emulators communicate with themainframe computer through a TN3270 server[b] using theTN3270 (RFC 1576) variant of theTelnet (RFC 495) protocol common onTCP/IP networks including theInternet, so special hardware is no longer required on machines with Internet access. Several vendors offered both coax and communications attached 3270 emulators and TN3270 clients as part of the same product.
One way of categorizing a 3270 simulator is by how it connects to the host.
Some 3270 simulators use a channel adapter to connect directly to the host. This is common in protocol converters or other situations where performance justifies the higher cost.
Some 3270 simulators use a coax adapter such as theIrma board to connect to a cluster controller.
Some 3270 simulators use asynchronous serial link to connect to a communications controller. UsingBSC requires less code, butSDLC withSNA allows more functionality.
Some 3270 simulators use a LAN interface to a cluster controller.
Contemporary 3270 simulators typically use TN3270 to connect to a TN3270 server on the host.
In 1983, IBM marketed theIBM 3270 PC, a bundled package including a PC, a graphics adapter, 3270 emulation software and coax interface card. 3270 emulators and TN3270 clients are also available from many third-party vendors likeAttachmate andEricom. Some solutions permitted a coax interface to be shared by workstations in a LAN.
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