Forging or Building packets in NodeJS - node.js

Question

I have to send a packet, when viewed in hex is:
0A 00 2C 01 23 00 0C 00 B3 01
0A 00 is the length which is 10.
2C 01 is a identifier 12c or could be a decimal packet id.
23 00 is a version of dec 35.
0C 00 is another version which is dec 12.
b3 01 is 435.
which is from different variables and configs.
var packet_id = 300;
var game_version = config.game.version; // 35 from config
var update_version = config.update.version; // 12 from config
var date_version = config.date.version; // 435 from version
The length is then calculated from the size with the length. Then build this buffer and send it..
But how do I do this? I also was thinking that I want to predefine packet structure and just enter parameters like:
packet("versionCheck", // name of packet structure (defined somewhere
300 , // the packet id on the structure
config.game.version, // the 2nd parameter for the versionCheck structure.....
............
I am trying to use the packet package by bigeasy for node but I can only make it work with Parsing, not with Building packets.

Answer 1

That's actually a pretty basic example of packet, since everything is static. Something like this might work:
function Packet (length, id, v1, v2, other) {
this._length = length;
this._id = id;
this._v1 = v1;
this._v2 = v2;
this._other = other;
}
Packet.prototype.toBuffer = function () {
var buffer = new Buffer(this._length);
buffer.writeUInt16LE(this._length, 0);
buffer.writeUInt16LE(this._id, 2);
buffer.writeUInt16LE(this._v1, 4);
buffer.writeUInt16LE(this._v2, 6);
buffer.writeUInt16LE(this._other, 8);
return buffer;
}
var packet = new Packet(10, 0x12c, 35, 12, 435);
console.log(packet.toBuffer());
Also for parsing you don't need anything special, just same as toBuffer, but with read instead of write methods