Nemp uses different web services. All online queries are Opt-In, so if Nemp want something to do in the internet, have have given your permission to do this before. This is want Nemp does online:

• Searching for updates. Nemp checkes regulary for Updates on my website gausi.de. You can stop that through "Settings > General settings"
• Scrobbeln. Nemp can scrobble your playlist to LastFM. When scrobbling is active, there will be a last.fm-logo  in the main window. Click on this logo, and you can stop this.
• Downloading cover art for player and coverflow. When Nemp can't find a cover for your tracks, Nemp can try to download it from LastFM. Stop it via "Settings > Player and Cover".  
• Playing webradio. Obvious, right?
• Sending data through the webserver. If the Nemp webserver is active, click on the webserver symbol , to stop it.
• Searhing for lyrics on http://lyrics.wikia.com. If you don't want this, just don't use this feature.
• Searching for additional tags for the tag cloud on LastFM. These tags describes the tracks more accurately tha just "Artist-Title-Album-Genre". Common used tracks are "singer-songwriter", "female fronted metal" , "male vocalists",... If you don't like this, don't use this feature.
• Determine your IP address. If you want to grant access to your library from outside your local network, your friends need to know your current IP address. Nemp uses a php-script on gausi.de for this purpose. However, amy other method will do it also.