Thanks for the answer! if i run from the prompt of windowsXP: java -jar sigar.jar ifconfig i got the normal response: MS TCP loopback interface l0: Link encap:local loopback .... RX packets: 11251 ... TX packets: 11251 ... collisions -1 RX bytes 3919679 (3.7M) TX bytes 3919679 (3.7M) I got the numbers running the program one time, but i always get similar results: with the same RX and TX packets, and the same RX and TX Bytes!