Port forwarding on Linux without iptables?

Ok here is the simple answer that should work, it's not rocket science but most people over complicate the answer and confuse all the new to Linux users.

ufw allow 2xxx

2xxx = what ever your port number is just type that command into your server terminal and your desired port is opened up.

There's a tiny, light resources program called redir which is pretty configurable.

apt-get install redir to install on Debian-based distributions.

redir :SRC :DEST will run in the background as a daemon.

xinetd supports a redirect attribute which will do what you want. As others have noted there are a number of programs which handle redirects.

Using xinetd or other program which uses the tcpwrappers library will allow you to apply access restrictions if and when it becomes necessary.

Use the tool called "socat", it is great tool for such things and it is already packaged in many linux distribution. Read about it here : http://www.dest-unreach.org/socat/doc/README

Port forwarding example with socat :

socat TCP4-LISTEN:80,fork TCP4:www.yourdomain.org:8080

This redirect all TCP connections on port 80 to www.yourdomain.org port 8080 TCP.

SSH Does port forwarding, so long as you can tunnel in an SSL connection.

I found small util called portfwd http://portfwd.sourceforge.net/ it does exactly what I need (TCP and UDP forwarding), homepage says it was last updated in 2002, but latest release is 2007, and it works on 2.6 kernel.

xinet/inetd. For e. g.:

redirect

Allows a tcp service to be redirected to another host. When xinetd receives a tcp connection on this port it spawns a process that establishes a connection to the host and port number specified, and forwards all data between the two hosts.

http://linux.die.net/man/5/xinetd.conf

What about rinetd ?
Its a daemon that redirects TCP connections. Have a look at the man page to see if it suits your needs: https://manpages.debian.org/unstable/rinetd/rinetd.8.en.html