If the buck stops with you when it comes to troubleshooting strange and bizarre application behavior, you’ll want to be able to use a packet capture tool effectively. Wireshark is ubiquitous; most network engineers use it. Wireshark has an active user and development community. Plus, there is a commercial variant through Riverbed if you care to go that route. Therefore, I view Wireshark as a safe packet analysis tool to spend time learning intimately.