Use 'screen' as a serial terminal emulator

Nov 14, '06 07:30:01AM

Contributed by: markstewart

I often have to do router configuration via a console port, so I use a Keyspan Serial Adapter to get access. Two problems then present themselves:

  1. ZTerm is a horrible Mac OS X app. It hasn't been updated in five years or so, and isn't a Universal Binary. The developer doesn't seem in any hurry to rectify the situation. It is not worth the shareware fee in its current form.
  2. Minicom requires installation of Fink or MacPorts and is overly complex.
Solution: Use screen, Terminal, and a little AppleScripting.

First, launch Script Editor and type/paste in the following code:

tell application "Terminal"
  do script with command "screen /dev/tty.KeySerial1"
  set number of rows of window 1 to 100
  set number of columns of window 1 to 80
  set background color of window 1 to "black"
  set normal text color of window 1 to "green"
  set custom title of window 1 to "SerialOut"
end tell
Compile and save as an app from within Script Editor, and you have a double-clickable application to launch a serial Terminal session. You may want to customize this slightly -- you can change the screen colors or number of columns or rows. You may also need to customize the screen command with a different device name if you are using something other than the Keyspan Serial Adapter (do an ls tty* of the /dev/ directory to get the right name).

screen uses Control-A to take commands directed to it. So type Control-A followed by Control-\ to exit your screen session. If you fail to do this and exit a Terminal session, you'll leave the screen session alive and the serial resource unavailable until you kill the screen session manually. man screen will show you further commands to send to a screen session.

If anyone can reply with a link to a tutorial on how to wrap an interactive Unix App in Cocoa, that would be the next step -- it would be nice to do this without involving Terminal. If you prefer to use Minicom, you could still use the AppleScript to wrap it into a nice launchable app -- use this older hint to find the right command line commands.

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