The content server logs won't have anything in them regarding CC failing to find calibre. That said, those logs moved when calibre V3 was released. In calibre, go to preferences / sharing over the net. Push the "Show logs" button. At the bottom of the window you will see the folder name where the logs are stored.
See here for how to get a calibre debug log. Start calibre with logging, attempt to connect with CC with "default settings" (no IP address), then quit calibre. In the normal case the debug log will contain lines like
Code:
SMART_DEV ( 225.14:223.151) run received broadcast ('localhost', ('192.168.120.4', 54982)) calibre wireless device client (on wallaby);8080,9090
SMART_DEV ( 228.15: 3.003) run attempt to open device socket
The received broadcast line tells you that calibre received CC's "are you there". The next line tells you that CC heard the response and is trying to connect.