Numbers are not sent in plain Two's compliment, as the stream is binary safe (contains no zero bytes) and consequently they have a slightly smaller range of possible values they can represent. See [EncodeNumber] for an algorithm to encode/decode numbers.

Numbers are not sent in plain Two's compliment, as the stream is binary safe (contains no zero bytes) and consequently they have a slightly smaller range of possible values they can represent. See [[EncodeNumber]] for an algorithm to encode/decode numbers.

There are three stages: Flipping, interleaving and "dickwinding". These only apply to the actual packet data (including the ID) and ''not'' the length bytes. For most client-to-server packets there is also a byte inserted immediately following the packet ID which we will refer to as the "counter".

There are three stages: [[#Flipping|Flipping]], [[#Interleaving|interleaving]] and "[[#Dickwinding|dickwinding]]". These only apply to the actual packet data (including the ID) and ''not'' the length bytes. For most client-to-server packets there is also a byte inserted immediately following the packet ID which we will refer to as the "[[#Counter|counter]]".

===Flipping===

All of the bytes in a packet are simply have their most significant bits flipped (i.e. XOR 0x80).

e.g. <pre>0x20 -> 0xA0

or

0x17 -> 0x97

</pre>

===Interleaving===

Packets are "woven" in to each-other using the following patterns.

Encoding e.g. <pre>abcde -> aebdc

or

abcdef -> afbecd

</pre>

This is the only step that requires different code for encoding and decoding.

Decoding e.g. <pre>abcde -> acedb

or

abcdef -> acefdb

</pre>

===Dickwinding===

This was named by Sausage and first implemented in the EOProxy project. There are two numbers sent from the server to the client on connect between 6 and 12 that represent a "send packet swap multiple" and a "receive packet swap multiple".

Any two bytes next to each other in the packet data that are divisible by that number are flipped.

<pre>Multiple = 5 (ASCII values: T=84, a=97, g=103, h=104, i=105, s=115, x=120)

"This is a gay six" -> "Thsi si a gay xis"</pre>

===Counter===

There are 2 values sent on connect, and with every [[PACKET_PING|ping packet]] that comes from the server, that give the client a "starting counter ID". A private counter is kept on both the server and the client that increases from 0 to 9 for each packet sent before looping back to 0. If a packet is sent with the wrong counter value (should be starting + loopingcount), the server usually disconnects them (however, no private servers implement this, and only some packets do on the official servers). When the "starting counter ID" is updated by a ping packet, the counter does not reset.