httptunnel - 3.3+dfsg-4 main

Creates a bidirectional virtual data stream tunnelled in
HTTP requests. The requests can be sent via a HTTP proxy
if so desired.
.
This can be useful for users behind restrictive firewalls. If WWW
access is allowed through a HTTP proxy, it's possible to use
httptunnel and, say, telnet or PPP to connect to a computer
outside the firewall.