RawCap is a free command line network sniffer for Windows that uses raw sockets.

Properties of RawCap:

- Can sniff any interface that has got an IP address, including 127.0.0.1 (localhost/loopback)
- RawCap.exe is just 17 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

Due to current limitations in the raw sockets implementations for Windows Vista and Windows 7 we suggest running RawCap on Windows XP. The main problem with raw socket sniffing in Vista and Win7 is that you might not receive either incoming packets (Win7) or outgoing packets (Vista).

If you only wanna sniff from localhost/loopback (127.0.0.1) though, then newer version of Windows actually works better than the old XP. When sniffing from localhost in Windows XP you will only be able to capture UDP and ICMP traffic, and not TCP. But TCP, UDP and ICMP packets can all be sniffed properly from localhost on both Windows Vista as well as Windows 7.