realmlib/net

A networking library for Realm of the Mad God.

Contents

• Install
• Use
  • Using the PacketIO class

Install

npm install @realmlib/net

Use

The realmlib networking module cannot be used on its own. It is designed to be used as a building block for larger RotMG projects which require an implementation of the RotMG networking protocol. Such project may include

• MITM proxies (such as KRelay or JRelay).
• Clientless applications (such as nrelay).

Using the PacketIO class

The PacketIO class provides an event based way of sending and receiving RotMG packets. It is very likely that a project which depends upon @realmlib/net will make use of the PacketIO class.

When a new PacketIO instance is constructed, it expects an object with 3 optional properties.

• socket - An instance of net.Socket
• rc4 - An object which contains an incoming RC4 key and an outgoing RC4 key.
• packetMap - An object which maps packet types to their IDs.

By default,

• socket will be initialised to undefined.
• rc4 will be initialised to an object containing the current RotMG incoming and outgoing RC4 keys.
• packetMap will be initialised to an empty object literal ({}).

If a socket is provided, the PacketIO instance will be immediately attached to that socket. A PacketIO instance can always be attached to a socket after constructed via the attach() method, so providing a socket to the constructor is not necessary.

The default values which are used for the rc4 property are set up for a clientless application. However, they are configurable to allow the PacketIO class to be used for other applications. For example, when building a MITM proxy, the PacketIO instance which listens to traffic coming from the server should use the incoming key for both the incoming and outgoing key configurations. The PacketIO instance which is listening to traffic coming from the client should use the outgoing key for both the incoming and outgoing key configurations.

import { PacketIO, INCOMING_KEY, OUTGOING_KEY } from '@realmlib/net';

const serverIO = new PacketIO({
  rc4: {
    incomingKey: INCOMING_KEY,
    outgoingKey: INCOMING_KEY,
  }
});

const clientIO = new PacketIO({
  rc4: {
    incomingKey: OUTGOING_KEY,
    outgoingKey: OUTGOING_KEY,
  }
})

The packetMap property is the most important one, as it allows the PacketIO instance to resolve packet ids to their types. This is necessary in order to create the right instances of packets when they are received, and to use the right id when sending packets.

The packetMap object is expected to bidirectional. That is, if the map contains the property

import { PacketMap, PacketType } from '@realmlib/net';

const packetMap: PacketMap = {
  FAILURE: 0,
};

it should also contain the reverse of that property.

const packetMap: PacketMap = {
  FAILURE: 0,
  0: PacketType.FAILURE,
};

Ideally, the packetMap should contain an entry for each property present in the PacketType enum. This will ensure that the PacketIO instance knows how to create any type of packet which it may receive. If some of the packet types are missing, the PacketIO will be unable to send those packets, and will not be able to create an instance of the packet when one is received.