Xlink Kai support

[codedwrench]

Hello CodedWrench,

thank you for your offer!
I would be very interested into more details on which interfaces could be used to communicate with XLink Kai from a Java world.

Jpcsp is supporting multiple levels of emulation for the network code:
1) HLE: high level PSP API's are emulated over ProOnline (or through Jpcsp's own protocol which mainly became obsolete with ProOnline)
2) mix of HLE and LLE: running everything in HLE, except for the networking code which can be run in LLE. I.e. the PSP original firmware networking code can be used to implement the high level PSP networking API's. This code is then interfacing with an HLE module sceWlan which is just responsible for abstracting the WLAN hardware. The complete network traffic is created by the PSP original code but transmitted through an HLE Java interface. Currently, sceWlan is using UDP for networking as Adhoc communication is not available from a Java world.
3) LLE: running everything in LLE. There, Jpcsp is emulating the WLAN hardware interface. Currently, this emulation is using UDP for networking. That part is very similar to the second scenario using sceWlan

I've tried XLink Kai on my own PSP using AdhocToUSB but couldn't really test it due to missing players in the Lobby. Do you know how the AdhocToUSB bridge is interfacing with XLink Kai? Is the bridge sending the PSP traffic over the Adhoc network on the PC side which is then picked up by XLink Kai like coming from a real PSP or is the bridge communicating over TCP/UDP? The TCP/UDP approach would be interesting for Jpcsp from Java.

Thank you for any support!

Okay, so on the first bit about the different types of emulation, I did spend the last 2 days or so trying all 3 types of emulation. In the last type of emulation you mentioned I almost have full trust that it will work after watching the traffic with wireshark for a bit, sadly I still wasn't able to connect 2 instances together, not sure what was going wrong.

As for the last bit, XLink Kai is taking the PSP traffic directly as is, whether through AdHocToUsb or a supported WiFi adapter. With AdHocToUSB it does so through a loopback adapter.

However, this method of doing things is no longer nessecary with XLink Kai, due to the DDS support that has been added not too long ago. I sent the following links on github as well, but let me just send them again for completeness:

https://www.teamxlink.co.uk/wiki/DDS_Protocol
https://github.com/dolphin-emu/dolphin/pull/8853

I've made a bit of a start on implementing this for JPCSP, (haven't gotten much further than adding the radiobuttons etc. though atm). But essentially for the traffic itself, all you need to do is send the data you're encapsulating in UDP now with the addition of e;e;[data] in the payload, where [data] is the original payload ofcourse.

Also, CrunchBite did find something in the MAC address generation part that is a bit of an issue, there are some PS2 MACs generated:
https://github.com/jpcsp/jpcsp/commit/71...t-43855791

In addition to that, when you start connecting to XLink Kai you would have to send:

connect;locally_unique_identifier;application_name;optional_padding

So for example:
connect;jpcsp1;JPCSP;

And when disconnecting:
disconnect;jpcsp1;JPCSP;

XLink Kai will also occasionally send keepalives, where you need to respond with the same in the form of:
keepalive;

If you want the XLink Kai chat to show up in JPCSP that is also supported, but for that I would refer you to that link I sent you before.