prtunnel tunnels TCP connections through an HTTP or SOCKS5 proxy server.
It is useful if you're behind such a proxy and want to use a program
that doesn't have native proxy support.

It's developed on Slackware Linux and OpenBSD (both x86), and should work
on any other Unix-like system.

prtunnel was written by Josh Beam <josh@joshbeam.com> and is distributed under
a BSD-style license (see prtunnel.h or any other source file for the exact
terms). The latest version can be found at
http://joshbeam.com/software/prtunnel


Usage
-----
  prtunnel [options] <local port> [<remote host> <remote port>]

<local port> is the local port you want prtunnel to listen to; <remote host>
is the name or address of the remote system you want to connect to;
<remote port> is the port of the service you want to use on <remote host>.

If run without the <remote host> and <remote port> arguments, prtunnel
will accept SOCKS4/SOCKS5 commands from the client to determine the
remote server to connect to.

Options:
  -D                Run as a daemon. prtunnel will run in the background
                    and accept multiple TCP connections with this option.
  -V                Verbose output (prints all data transferred to standard
                    output)
  -c                Use color to differentiate between incoming and outgoing
                    data in verbose output; without this, each line of outgoing
                    verbose output will begin with ">>> " and incoming output
                    with "<<< "
  -6                Enables IPv6 mode. This doesn't affect the way outgoing
                    connections are made with the direct/direct6 tunneling
                    modes; direct will always connect with IPv4 and direct6
                    will always connect with IPv6.
  -t <tunnel mode>  Set tunneling mode; http (default), socks5, direct and
                    direct6 are supported. With http and socks5, you must
                    specify the address of an http/socks5 proxy to use.
                    direct will make prtunnel connect directly to the remote
                    host specified; direct6 does the same, but with IPv6
                    instead of IPv4.
  -H <proxy host>   Name or address of the proxy server you wish to use
  -P <proxy port>   Port that the proxy server uses (8080 default for http,
                    1080 default for socks5)
  -T <address>      Add a trusted address. For security reasons, only localhost
                    is trusted by default. Only connections from trusted
                    addresses are allowed. You can specify an address itself
                    (like 10.0.0.1), or in the form of address/bitcheck, where
                    bitcheck is the number of leading bits to compare; for
                    example, 10.0.0.0/24 would mean any address in the range
                    of 10.0.0.0 to 10.0.0.255.
  -u <username>     Set proxy authentication username
  -p <password>     Set proxy authentication password
  --password-prompt
                    Prompt for proxy username and password
  --http-1.0        Use HTTP/1.0 instead of HTTP/1.1 for HTTP connections
  --telnet-keep-alive <interval>
                    Causes prtunnel to send keep-alive data at the
                    specified interval, using the telnet NOP command
  --crlf-keep-alive <interval>
                    Causes prtunnel to send keep-alive data at the
                    specified interval, using a CRLF
  --irc-auto-pong   Causes prtunnel to automatically respond to PING commands
                    sent by IRC servers
  --timeout <time>
                    Allows you to set a client socket timeout; if no data
                    is recieved from the client for <time> seconds, the
                    connection will be closed
  --server-timeout <time>
                    Allows you to set a server socket timeout; if no data
                    is recieved from the remote host for <time> seconds,
                    the connection will be closed
  -h, --help        Print help message
  -v, --version     Show version information

Here's an example:
  prtunnel -H proxy 6667 irc.freenode.net 6667
After starting prtunnel like this, you could then point an IRC client to
127.0.0.1, and prtunnel will attempt to connect you to irc.freenode.net
via the HTTP proxy server on a system named "proxy".