About Engine IO V3 Clients compability

[tenmo2003]

Hi, this repository seems to be a descendant of https://github.com/mrniko/netty-socketio. I want to ask about a specific commit 5e56faa. This commit removed the Engine IO's packet type byte strip in PacketDecoder, causing the payload received in user-end has an additional byte (e.g. '4') in front. Is there any reason behind this because it can easily be fixed with EIO version check stripping? I don't really want to have to manually check and strip this byte

[sanjomo]

@NeatGuyCoding can you please review this one?

[sanjomo]

@tenmo2003 is not this also done in the parent project? what exactly the problem you are facing due to this? can you add more details with minimum reproducible example ?

[tenmo2003]

Yes it is done in the parent project. But as the parent project is kinda archived now, I want to ask if you guys know the reason behind it, as you guys seem to be earlier maintainers. My case is simple, I updated from 1.7.17 to 2.0.13, and my code throws an Exception as they are reading an extra '4' (EIO message type) first byte. After adding this code snippet I attached, it worked normally again.

This only happens with binary frames as in newer versions the whole binary attachment is base64 encoded with no modification compare to the stripping come from earlier version (ref commit 5e56ffa0):

[tenmo2003]

Yeah and for more detail, in version 2.0.13, this problem only occurs for EIOv3 clients, as in EIOv4 spec, clients no longer prefix binary payload with type byte anymore

For binary data the encoding is identical. When sending binary data, the packet type id is sent in the first byte of the binary contents, followed by the actual packet data.

from https://github.com/socketio/engine.io-protocol/tree/v3

Binary payloads are sent as is, without modification.

from https://github.com/socketio/engine.io-protocol/tree/main