Skrillax Universal Patch Server

This is a minimal Gateway Server implementation for Silkroad Online which allows patching both ways; update and downgrade. I.e. using this, the client can go from v1.594 to v1.595 OR v1.593, depending on what the desired version is. To properly use this, you most likely need a special patcher tool that can connect to the patch server and handle patch selection for it.

Warning

Work In Progress

This is very much a work in progress. There's no error correction, error messages, or other helpful stuff provided by the server. It will probably break, so treat it with care.

Requirements

What you need additionally (in short):

• Full patch content for each version
• Simple file server

For the Universal Patch Server to work, it needs all files with their content for all the versions available through the server, in addition to the full file list for the base version. The latter part isn't strictly necessary, but could cause files to remain unpatched when downgrading.

The server needs a folder called patches, which should contain a directory for each available patch version¹. Inside each patch folder should be the individual files making up the patch using the same paths and filenames as provided by the official patch server. The files should also already be compressed, as this patch server does not serve the files themselves.

You additionally need a normal (static) file server that can serve the actual files to patch to the client. Any server is fine - nginx, miniserve, whatever works.

Usage

Create a directory and place both the patches directory and the patcher executable inside. From within that directory, run the patcher. The patcher will open sockets on ports between 32000 and 32999², so make sure these are accessible from the outside and unused.

Start the file server and configure it to serve the content inside the patches directory from port 80 (this generally elevated privileges).

The rest should be up to the client patcher.

How it works

Silkroad Online normally does not support downgrading by itself, as it's not really something that they want to do, as it's simpler to just update and revert the changes. However, the client doesn't actually care if the new version is larger or smaller than the current version. It can be tricked into "updating" to an older version, by simply telling it there's an update and sending it an older version as the new one.

We then only need a way for the client to indicate which version it wants to change to. This is done through the port. When a client connects to the port 32594 we take it as a request to patch to version 594. In the patching process, the client then sends its current version, which we can compare to what version it wants. We can then diff the files between the two versions and send the new files accordingly.

The only problem being the client will always use port 15779 for the gateway. To work around that, we need a custom patcher that will temporarily run a proxy that will pick the right port instead, such that the client still connects to 15779 and is then forwarded to the corresponding port for the version.

Footnotes

1. If the client reports v1.594, the patch version is 594. This is the value the client sends as its version. ↩

2. For each version available, the patcher will open a port given the pattern 32XXX where XXX is the version. For version 594 the port would be 32594. ↩