| icmptunnel encapsulates data in ICMP frames. Its usual mode of operation is TCP/IP forwarding, where one icmptunnel will be set up on a blocked machine (behind a firewall) listening on one TCP/IP port. The other icmptunnel will be set up on a nonblocked machine (somewhere on the Internet) connected to a local service. Data received on the blocked machine's TCP/IP socket will be encapsulated in an ICMP packet of users choice (ICMP_ECHO, ICMP_ECHOREPLY, ICMP_TIMESTAMP, etc..) and sent to the nonblocked machine. |