Node.js websockets client-server packets - node.js

Question

I'm writing a client and server who obviously has to work with each other. In both the client and the server, I have a class to construct messages. These messages are sent over through websockets.
Now the problem lies in the method I use to construct messages. I make use of the Buffer class and both the read...BE functions and the write...BE functions. Somehow, the data written on the client doesn't correspondent with the data read on the server.
One example of a message sent to the server is the LOGIN message:
import ClientMessage from "../../protocol/ClientMessage";
import { LOGIN } from "../../protocol/OpCodes/ClientOpCodes";
export default class RequestLogin extends ClientMessage {
constructor(username: string, look: string) {
super(LOGIN);
this.appendString(username);
this.appendString(look);
}
}
The LOGIN from the opcodes is equal to 1, and the message ID should be 1.
Next, once a login button is pressed, this code is executed:
this.game.communicationManager.sendMessage(new RequestLogin(username, look));
This is the sendMessage function:
sendMessage(message: ClientMessage) {
if (this.client.connected) {
//console.log('Sent [' + message.id + ']: ' + message.constructor.name);
this.client.send(message.getPacket());
}
}
Last, this is the ClientMessage class:
export default class ClientMessage {
body: Buffer;
pos: number;
constructor(id: number) {
this.body = Buffer.alloc(512);
this.pos = 0;
this.appendShort(id);
}
appendShort(i: number) {
this.body.writeInt16BE(i, this.pos);
this.pos += 2;
}
appendInt(i: number) {
this.body.writeInt32BE(i, this.pos);
this.pos += 4;
}
appendString(str: string) {
this.appendShort(str.length);
this.body.write(str, 'utf8');
this.pos += str.length + 2;
}
getPacket(): string {
return this.body.toString();
}
}
(I'm aware 512 is a bit overkill, but I assume it doesn't matter really in terms of reading).
Now, going over to the server, the ClientMessage on the server side looks like this:
export default class ClientMessage {
packet: Buffer;
id: number;
pos:number;
constructor(packet:string) {
this.packet = Buffer.from(packet);
this.pos = 0;
this.id = this.getShort();
}
getShort(): number {
const value = this.packet.readInt16BE(this.pos);
this.pos += 2;
return value;
}
getInt(): number {
const value = this.packet.readInt32BE(this.pos);
this.pos += 4;
return value;
}
getString(): string {
const strlen = this.getShort();
const value = this.packet.toString('utf8', this.pos, this.pos + strlen);
this.pos += strlen;
return value;
}
}
This is the callback for this.ws.on('message'
onDataArrival(message:string): any {
const clientMessage:ClientMessage = new ClientMessage(message);
console.log(clientMessage.id);
console.log(clientMessage.getString());
}
Oddly enough, the id is already wrong. Where it should be 1 (cause the LOGIN equals to 1), clientMessage.id has 26738 as value which is WAY higher. I'm not sure what I'm doing wrong or what I'm missing. (of course, the string is incorrect as well)

Answer 1

Found it out already. The problem was my appendString on the clientside.
appendString(str: string) {
this.appendShort(str.length);
this.body.write(str, this.pos, 'utf8');
this.pos += str.length;
}
I had to write the string at the correctb position of course.