run `echo '1+1' | node parent.js`

child.js

var stdin = process.stdin;
stdin.resume();
stdin.on('data', function (data) {
  console.log('GOT STDIN FROM PARENT', data + '')
})

//
// Keep it alive
//
setInterval(function() {}, 10000)

parent.js

var spawn = require('child_process').spawn;

var code = '';
process.stdin.resume();
process.stdin.on('data', function (data) {code += data})
process.stdin.on('end', function () {
  console.error('WRITING DATA')
  var child = spawn('node',['child.js']);
  child.stdout.on('data', function (data) {
    console.log('CHILD.STDOUT', data + '')
  })
  child.stderr.on('data', function (data) {
    console.log('CHILD.STDERR', data + '')
  })
  child.stdin.write(code)
})

//Just keep this alive...
setInterval(function () {}, 10000)