Multiple Screens¶

Blessed supports the ability to create multiple screens. This may not seem useful at first, but if you're writing a program that serves terminal interfaces over http, telnet, or any other protocol, this can be very useful.

Server Side Usage¶

A simple telnet server might look like this (see examples/blessed-telnet.js for a full example):

var blessed = require('blessed');
var telnet = require('telnet2');

telnet({ tty: true }, function(client) {
  client.on('term', function(terminal) {
    screen.terminal = terminal;
    screen.render();
  });

  client.on('size', function(width, height) {
    client.columns = width;
    client.rows = height;
    client.emit('resize');
  });

  var screen = blessed.screen({
    smartCSR: true,
    input: client,
    output: client,
    terminal: 'xterm-256color',
    fullUnicode: true
  });

  client.on('close', function() {
    if (!screen.destroyed) {
      screen.destroy();
    }
  });

  screen.key(['C-c', 'q'], function(ch, key) {
    screen.destroy();
  });

  screen.on('destroy', function() {
    if (client.writable) {
      client.destroy();
    }
  });

  screen.data.main = blessed.box({
    parent: screen,
    left: 'center',
    top: 'center',
    width: '80%',
    height: '90%',
    border: 'line',
    content: 'Welcome to my server. Here is your own private session.'
  });

  screen.render();
}).listen(2300);

Once you've written something similar and started it, you can simply telnet into your blessed app:

$ telnet localhost 2300

Creating a netcat server would also work as long as you disable line buffering and terminal echo on the commandline via stty: $ stty -icanon -echo; ncat localhost 2300; stty icanon echo

Or by using netcat's -t option: $ ncat -t localhost 2300

Creating a streaming http 1.1 server than runs in the terminal is possible by curling it with special arguments: $ curl -sSNT. localhost:8080.

There are currently no examples of netcat/nc/ncat or http->curl servers yet.

The blessed.screen constructor can accept input, output, and term arguments to aid with this. The multiple screens will be managed internally by blessed. The programmer just has to keep track of the references, however, to avoid ambiguity, it's possible to explicitly dictate which screen a node is part of by using the screen option when creating an element.

The screen.destroy() method is also crucial: this will clean up all event listeners the screen has bound and make sure it stops listening on the event loop. Make absolutely certain to remember to clean up your screens once you're done with them.

A tricky part is making sure to include the ability for the client to send the TERM which is reset on the serverside, and the terminal size, which is should also be reset on the serverside. Both of these capabilities are demonstrated above.

For a working example of a blessed telnet server, see examples/blessed-telnet.js.