3270.rst (2315B)
13270 devices 2============ 3 4The 3270 is the classic 'green-screen' console of the mainframes (see the 5`IBM 3270 Wikipedia article <https://en.wikipedia.org/wiki/IBM_3270>`__). 6 7The 3270 data stream is not implemented within QEMU; the device only provides 8TN3270 (a telnet extension; see `RFC 854 <https://tools.ietf.org/html/rfc854>`__ 9and `RFC 1576 <https://tools.ietf.org/html/rfc1576>`__) and leaves the heavy 10lifting to an external 3270 terminal emulator (such as ``x3270``) to make a 11single 3270 device available to a guest. Note that this supports basic 12features only. 13 14To provide a 3270 device to a guest, create a ``x-terminal3270`` linked to 15a ``tn3270`` chardev. The guest will see a 3270 channel device. In order 16to actually be able to use it, attach the ``x3270`` emulator to the chardev. 17 18Example configuration 19--------------------- 20 21* Make sure that 3270 support is enabled in the guest's Linux kernel. You need 22 ``CONFIG_TN3270`` and at least one of ``CONFIG_TN3270_TTY`` (for additional 23 ttys) or ``CONFIG_TN3270_CONSOLE`` (for a 3270 console). 24 25* Add a ``tn3270`` chardev and a ``x-terminal3270`` to the QEMU command line:: 26 27 -chardev socket,id=ch0,host=0.0.0.0,port=2300,wait=off,server=on,tn3270=on 28 -device x-terminal3270,chardev=ch0,devno=fe.0.000a,id=terminal0 29 30* Start the guest. In the guest, use ``chccwdev -e 0.0.000a`` to enable 31 the device. 32 33* On the host, start the ``x3270`` emulator:: 34 35 x3270 <host>:2300 36 37* In the guest, locate the 3270 device node under ``/dev/3270/`` (say, 38 ``tty1``) and start a getty on it:: 39 40 systemctl start serial-getty@3270-tty1.service 41 42 This should get you an additional tty for logging into the guest. 43 44* If you want to use the 3270 device as the Linux kernel console instead of 45 an additional tty, you can also append ``conmode=3270 condev=000a`` to 46 the guest's kernel command line. The kernel then should use the 3270 as 47 console after the next boot. 48 49Restrictions 50------------ 51 523270 support is very basic. In particular: 53 54* Only one 3270 device is supported. 55 56* It has only been tested with Linux guests and the x3270 emulator. 57 58* TLS/SSL is not supported. 59 60* Resizing on reattach is not supported. 61 62* Multiple commands in one inbound buffer (for example, when the reset key 63 is pressed while the network is slow) are not supported.