The process that makes Bonjour work is mDNSResponder, located in /usr/sbin. /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist invokes mDNSResponder on boot. One of the easiest ways to troubleshoot issues you think are related to Bonjour is to temporarily disable the mDNSResponder: launchctl unload -w /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist To enable it: launchctl load -w /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist In addition to basic starting and stopping of the mDNSResponder, when troubleshooting any service, one should always look at logs. Log events are logged to the standard syslog facility and so are available via Console. These are locate at /var/log/system.log. Searching for mDNSResponder errors in system.log can also be done from the command line using: cat /var/log/system.log | grep mDNSResponder Or interactively so…