nodejs stream transform, uppercase

transform.js

var Transform = require('stream').Transform;

/// Server:

var server = require('net').createServer();

function onConnection(socket) {

  /// Create the transform stream:
  var uppercase = new Transform({
    decodeStrings: false
  });

  uppercase._transform = function(chunk, encoding, done) {
    done(null, chunk.toUpperCase());
  };

  /// pipe socket
  socket.setEncoding('utf8');
  socket.pipe(uppercase).pipe(socket);
}

server.on('connection', onConnection);

server.listen(3000);