Port mapping utility

[highs008]

I'm looking for an utility to route incoming as well as outgoing TCP/UDP ports to another port.

For example; two hosts connected to the internet. Host A wants to send TCP data over port 80 to host B. This action is intercepted and instead of using port 80, port 1000 (for example) will be used.

Then this packet will arrive at host B. It sees port 1000 is used and will reroute this packet to port 80. Finally this packet will be delivered to higher layers over it's new port.

Any suggestions?

 

[dilettante]

Can't think of one right now, but I suspect they're out there.

This would involve a utility on each machine though.

[client]--80-->[utility]--1000--+
                                |
[server]<--80--[utility]<-1000--+

For moderate-performance needs this could even be built in VB fairly easily - though TCP connections might prove a little easier than handling UDP datagrams. Still no biggie.

Somebody must have built one of these already.

 

[highs008]

I know I have to use two utilities, that's not the problem. But I don't think it will be easy to implement this in VB. Sure, if I want to redirect ports not already in use, it would be an fairly easy job, but I want to redirect *known* ports and they are definately already open.

For example UDP ports 138, 139. The only way (as far as I know) is to use a utility that functions as a new layer between the physical and the datalink layer. If there is an utility that is able to do this I would greatly appreciate it...

Hope this helps...

 

[dilettante]

Yeah, you're right of course.

The only "easy" way I can think of to do this is to run the remapper on the "client" side on a third machine - one that doesn't have listeners bound to ports such as 138 and 139 already.

I'm assuming you want the client machine to basically be "clean" (running all its normal services).

Even if you were wedged in at the IP level someplace... hmm. You want to intercept things like outbound UDP 138 & 139.

This sounds a lot like a VPN pseudo-adapter.

Anybody else?

 

[Guest_imported]

IT's very easy, you can use a port mapping or Advance NAT utility. Look at WinRoute (windows) or the IProute (Linux). The latter comes default with Suse Linux and can also be download for free.

In addition if you have a cisco router or firewall, you can setup a rule on the device.

Contrary to what earlier replies state. YOU NEED NO HAVE THIS ON EVERY CLIENT -- just on the gateway machine.