Yrurtj

With socat on the server:

socat tcp-listen:8001,reuseaddr,fork tcp:localhost:8000

By default, socat will listen on TCP port 8001 on any IPv4 or IPv6 address (if supported) on the machine. You can restrict it to IPv4/6 by replacing tcp-listen with tcp4-listen or tcp6-listen, or to a specific local address by adding a ,bind=that-address.

Same for the connecting socket you're proxying to, you can use any address in place of localhost, and replace tcp with tcp4 or tcp6 if you want to restrict the address resolution to IPv4 or IPv6 addresses.

Note that for the server listening on port 8000, the connection will appear as coming from the proxy (in the case of localhost, that will be localhost), not the original client. You'd need to use DNAT approaches (but which requires superuser privileges) for the server to be able to tell who's the client.

Using the traditional nc is the easiest solution:

nc -l -p 8001 -c "nc 127.0.0.1 8000"

This version of nc is in the netcat-traditional package on Ubuntu. (You have to update-alternatives or call it nc.traditional.)

Note that in contrast to ssh this is not encrypted. Keep that in mind if you use it outside one host.

OpenBSD netcat is available by default on Linux and also on OS X.

OSX:

mkfifo a

mkfifo b

nc 127.0.0.1 8000 < b > a &

nc -l 8001 < a > b &

Linux:

mkfifo backpipe

nc -l 12345 0<backpipe | nc www.google.com 80 1>backpipe

An alternative that works on OS X bash is to use a bidirectional pipe. It may work on other Unixes:

nc 127.0.0.1 8000 <&1 | nc -l 8001 >&0

Quoting a David Spillett's answer on ServerFault

rinetd should do the job, and a Windows binary for it can be had from http://www.boutell.com/rinetd/ (for anyone looking for the same thing under Linux, rinetd is in the standard repositories of just about every distro so can be installed with "apt-get install rinetd" or "yum install rinetd" or similar)

It is a simple binary that takes a configuration file in the format

bindaddress bindport connectaddress connectport

For example:

192.168.1.1 8001 127.0.0.1 8000

or

0.0.0.0 8001 127.0.0.1 8000

if you want to bind the incoming port to all the interfaces.

iptables -t nat -A PREROUTING -p tcp --dport <origin-port> -j REDIRECT --to-port <destination-port>



service iptables save

service iptables restart

this is a new way to tunnel two udp port on server:
https://github.com/9crk/udpeer

udpeer 8001 8002

test:
nc -u xxxx.com 8001
nc -u xxxx.com 8002