Mocha TN3270 Help

Making a session

There are three ways, you can use to connect to an IBM Mainframe:

  • Select the connect icon in the tool bar.
  • Use menu - file - connect or edit/new session.
  • Give the IP address for the host as a parameter to the program.
If no session has previous been configured, and connect is selected, the normal connect dialog is shown:

  • Name: A session can be given any name, which will make it easier to remember it. The session name is also shown in the title bar, when the session is active
  • Host name: Name of the IBM Mainframe. Either a TCP/IP address as or a DNS name.
  • Port number:Port number for the session. As default TN3270 uses port 23 and with SSL port 992
  • SSL: Enable SSL encryption
  • Terminal size: 4 types of terminals are supported:
    IBM-3278-2-E : 24x80 color display
    IBM-3278-3-E : 32x80 color display
    IBM-3278-4-E : 43x80 color display
    IBM-3278-5-E : 27x132 color display
  • Auto Login:Use these fields to define an user id and a password for the Sign On screen on the IBM Mainframe.
    Notice there is not much security involved doing it! It could be an idea to contact the system administrator to verify it is your company politic to have open access to the system without any password security.
  • Exit on session termination:If the IBM Mainframe terminates the session, Mocha TN3270 will close without any notification.
  • Confirm exit:If mocha TN3270 is terminated (maybe with ALT F4), and a session is active, an exit confirm box will be shown.
  • Send keep alive:The TCP layer is designed to keep the connection alive, but with network problems, this option can be used to send extra keep alive packets with 10 second intervals.
  • Connect to this host at program start: If enabled, a session will be started, when the program is loaded.

Status line

The status line shows the current status for the 3270 session. It is build on 6 fields:

  • Connection state:
    ONLINE : A session is active with an IBM Mainframe.
    ONLINE-SSL : A session using the SSL protocol is active with an IBM Mainframe.
    OFFLINE : No active session. Click here to make a new connection.
    RECORD : Recording a macro. Click here to stop recording.
    ASCII : Telnet session has not yet entered the 3270 mode.
  • State:
    X-WAIT : Waiting on IBM Mainframe. A numer after X-WAIT is the number of bytes waiting in the type ahead buffer
    X-WRONG INPUT: If trying to type characters at a protected location on the screen.
    X-NUMERIC ONLY: Field is defined as numeric only, and a normal character as "ABC" input is rejected. Can be ignored with option in menu - Tools - Options -Terminal
  • Last function key pressed.
  • Insert mode.
  • Cursor position (y,x).

If moving the mouse over the status bar, tool tips will be shown.

Using the mouse

There are 3 ways to select text in the screen:

  • move the mouse pointer over an area of the screen, while holding down the left mouse button
  • put the mouse cursor over a word and then double-clicking on the word with the left mouse button.
  • hold down shift + move the cursor to select a text.
Hereafter use function copy to copy the text data to the clipboard.

If menu - edit - Ctrl C+v as copy/paste is enabled, it is possible to use Ctrl+C for easy access for the Copy function.

Changing font size

The screen font size follows the size of the window. The program will always try to use the largest possible font size. If a larger font is wanted, use the mouse to pull the current TN3270 window to a larger size.

The font size for printing can be defined in

menu - Tools - Options - printer

Configuration files

The configuration, including the keyboard layout is stored in a single file user.config (XML format). The file location can be viewed in

menu - Tools - Options - Configuration - Defaults

Ctrl+C and Ctrl+V as copy/paste

As default the CTRL keys are used as single function keys. Left CTRL is RESET and Right CTRL is ENTER. If menu - edit - Ctrl C+v as copy/paste is enabled, CTRL+C and CTRL+V will work as normal copy/paste functions.

SSL (Secure Socket Layer)

With the Secure Sockets Layer (SSL) protocol, it is possible to establish a secure connection between the IBM Mainframe and a Telnet client. Mocha TN3270 uses the SSL/TLS layer included with the Windows OS.


No validation of the Certificate from the IBM Mainframe. A Certificate is used for the IBM Mainframe to proving its identity. We have selected not to include such an option, as to keep the use of SSL as simple as possible. For most customers the main reason to select the SSL protocol, is to make the data traffic secure.