client_echo.js

var mc = require('minecraft-protocol');

if(process.argv.length < 4 || process.argv.length > 6) {
  console.log("Usage : node echo.js <host> <port> [<name>] [<password>]");
  process.exit(1);
}

var client = mc.createClient({
  host: process.argv[2],
  port: parseInt(process.argv[3]),
  username: process.argv[4] ? process.argv[4] : "echo",
  password: process.argv[5]
});

client.on('connect', function() {
  console.info('connected');
});
client.on('disconnect', function(packet) {
  console.log('disconnected: '+ packet.reason);
});
client.on('chat', function(packet) {
  var jsonMsg = JSON.parse(packet.message);
  if(jsonMsg.translate == 'chat.type.announcement' || jsonMsg.translate == 'chat.type.text') {
    var username = jsonMsg.with[0].text;
    var msg = jsonMsg.with[1];
    if(username === client.username) return;
    client.write('chat', {message: msg});
  }
});