A question about sockets...I think.

[Eternal]

Well said. That's exactly what I was saying. Looks like the whole DSL line issue has just clouded the picture a bit. So, to confirm, my DSL line is nothing to do with the problem, it was just highlighting the issue that I was not sending keep-alive packets correctly, hence the bot would not autoreconnect when my DSL line disconnected.

Thanks to the suggestions here, I have managed to fix the problem.