@fcl_itcs, srussell has included the app in his tag. It includes a scripted input for TCPDUMP
On my mac I open a terminal and type:
tcpdump -i en0 >> newLogFileName
Or for pcap format you could use:
tcpdump -i en0 -w NewLogFileName.pcap
Could you be more precise? What is "this app"? Dump of what? ...