Sending/receiving files over port 80

[eluser]n0xie[/eluser]
You are talking about exposing part of your database via a webservice. There are a lot of solutions which you can use, all with different pros and cons. Try googling around for: SOAP, REST and XML-RPC. And obviously PHP+Webservices. CI supports XML-RPC via libraries which you can read about here, but there is nothing stopping you from using any of the other techniques.