Ping Tunnel is a tool for reliably tunneling TCP connections over ICMP echo
request and reply packets (commonly known as ping requests and replies). It
is useful for evading firewalls that, for whatever reason, prevent outgoing
TCP connections, but allow in- and outgoing ICMP packets. The tunnel works
by having a proxy run on a machine ping-able from the inside of the
firewall, with the client running on the local machine from which TCP access
The following example illustrates the main motivation in creating ptunnel:
Setting: You're on the go, and stumble across an open wireless network.
The network gives you an IP address, but won't let you send TCP or UDP
packets out to the rest of the internet, for instance to check your mail.
What to do? By chance, you discover that the network will allow you to ping
any computer on the rest of the internet. With ptunnel, you can utilize
this feature to check your mail, or do other things that require TCP.