On some Linux systems you can use the ipchains REDIRECT mechanism to redirect from one port to another inside the kernel (if ipchains is not available, then usually iptables is):

# /sbin/ipchains -I input --proto TCP --dport 80 -j REDIRECT 8080

This command instructs the system as follows: "Insert into the kernel's packet filtering the following as the first rule to check on incoming packets: if the protocol is TCP and the destination port is 80, redirect the packet to port 8080". Be aware that your kernel must be compiled with support for ipchains (virtually all stock kernels are). You must also have the ipchains command-line utility installed. You can run this command at any time, preferably just once, since it inserts another copy of the rule every time you run it.

On many Linux systems you can use the iptables REDIRECT mechanism to redirect from one port to another inside the kernel (if iptables is not available, then usually ipchains is).

You need to add something like the following to the startup scripts or your firewall rules:

# /sbin/iptables -t nat -I PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080

The underlying model of iptables is different from ipchains, so the forwarding normally happens only to packets originating off-box. You also need to allow incoming packets to port 8080 if you use iptables as a local firewall.

Be careful to place rules like this one early in your input chain. Such rules must precede any rule that accepts the packet, otherwise the redirection won't occur. You can insert as many rules as required if your server needs to listen on multiple ports, as for HTTPS.

SetUID is a technique that uses Unix-like file system access right to allow users to run an executable that would otherwise require higher privileges.

Jetty's SetUID module allows you to run Jetty as a normal user even when you need to run Jetty on port 80 or 443. The module is hosted as part of the Jetty ToolChain project and it is released independently from Jetty itself (and as such it has a different version than Jetty releases). You can find the source code here, while the Maven coordinates are:

<dependency>
    <groupId>org.eclipse.jetty.toolchain.setuid</groupId>
    <artifactId>jetty-setuid-java</artifactId>
</dependency>

Jetty's SetUID module provides an implementation for Linux and OSX.

Since the SetUID feature requires native code, you may need to build it for your environment.

In order to use Jetty's SetUID module, you need to copy file jetty-setuid-java-<version>.jar into $jetty.home/lib, and make sure that the native library file (for Linux this file is called libsetuid-linux.so) is present in the native library path of the JVM (see also Configuring Jetty for SetUID).

Jetty's SetUID module also provides a default configuration file in the Jetty XML format, in file jetty-setuid-java-<version>-config.jar. This file can be unjarred in $jetty.home/lib and it will provide a $jetty.home/etc/jetty-setuid.xml file that you can customize. Alternatively, follow the next section that specifies how to create a Jetty XML config file for Jetty's SetUID.

<?xml version="1.0"?>
<!DOCTYPE Configure PUBLIC "-//Mort Bay Consulting//DTD Configure//EN" "http://jetty.mortbay.org/jetty/configure_9_0.dtd">
<Configure id="Server" class="org.eclipse.jetty.setuid.SetUIDServer">
  <Set name="umask">UMASK</Set>
  <Set name="uid">USERID</Set>
</Configure>

With modern Linux flavours, inetd has a newer, better big brother xinetd, that you can use to redirect network traffic. Since xinetd is driven by text files, all you need is a text editor. For detailed information, see http://www.xinetd.org/.

There are two ways to give xinetd instructions:

The format is the same; if you have a look at the file/directory, you will get the picture.

The following entry redirects all inward TCP traffic on port 80 to port 8888 on the local machine. You can also redirect to other machines for gimp proxying:

service my_redirector
{
 type = UNLISTED
 disable = no
 socket_type = stream
 protocol = tcp
 user = root
 wait = no
 port = 80
 redirect = 127.0.0.1 8888
 log_type = FILE /tmp/somefile.log
}

Solaris 10 provides a User Rights Management framework that can permit users and processes superuser-like abilities:

usermod -K defaultpriv=basic,net_privaddr myself

Now the myself user can bind to port 80.

Refer to the Solaris 10 and Solaris 11 Security Services documentation for more information.