RawCap is a free command line sniffer for network activity on Windows.

Properties of RawCap: Can sniff any interface that has got an IP address, including 127.0.0.1 (localhost/loopback) RawCap.exe is just 23 kB No external libraries or DLL's needed other than .NET Framework 2.0 No installation required, just download RawCap.exe and sniff Can sniff most interface types, including WiFi and PPP interfaces Minimal memory and CPU load Reliable and simple to use