Furry stuff, oekaki stuff, and other stuff.
You are not logged in.
That makes sense, because SecFilterEngine is a setting for mod_security, a popular security module for web servers. I'll keep this in mind should someone else run into this problem.
My best guess is that the server doesn't like files uploaded as octet streams -- it wants multipart encoding, instead. If Chibi Paint is able to upload files with "SecFilterEngine On", but PaintBBS and ShiPainter are not, then the encoding is the problem.
Haven't tried Chibi Paint.. I did find a fix though, though I dunno if it'll cause any problems eventually; I used .htaccess and "SecFilterEngine Off" in the directory and that seemed to work. :x
I've never seen this before, either.
HTTP 406 means "not acceptable", and occurs when the server thinks it can't send a response in a way that the client can understand. This could be because ShiPainter does not transmit data with the "Accept" HTTP property, which specifies which data types the client can understand (such as "text/html" or "application/xml") . ShiPainter only transmits "Accept-Language". This is just a guess, though. Chibi Paint doesn't transmit an "Accept" property, either. Does Chibi Paint work?
It's possible that the server has a very strange security policy designed to kick robots, but that's also just a guess. I've never seen a server refuse to serve "text/plain" over a socket before, because everything supports text/plain by default.
Unfortunately, I don't have access to the source code for ShiPainter, so we can't really test anything. You could try asking a sys admin. Tell them the applet sends data as a chunked octet stream, and expects a text/plain response, but the server is sending HTTP 406 instead.
I tried installing an oekaki somewhere and it went perfectly, until I tried to save an image.. To which it gives me "Server returned HTTP response code: 406 for URL: ___ SendE" and it seemed to involve shiget.php. Any idea as to what's going on? D: I've never seen this before.