1

I am used to forwarding a remote service port on localhost using ssh like:

ssh -L 2181:localhost:2182 user@server (forward remote host port 2182 to local port 2181)

now, from the machine I ssh to, I am trying to reach a tcp service and forward the response to my local machine:

local-machine:2181 <-- SSH --> remote-machine:2182 <-- netcat/named pipe --> service:2181

Note: I do not have direct access to the service machine, I only have access to the network through the machine I SSH to.

I was trying to use netcat with a named pipe:

On the remote-machine:

mkfifo fifo
nc -k -l 2182 <fifo | nc service 2181 >fifo

On local machine: echo message | nc localhost 2181

but that doesn't seem to work.

I also tried, on remote-machine nc -k -l 2182 0<fifo | nc service 2181 1>fifo

without luck

On the remote machine nc -k -l 2182 outputs the message I send from the local-machine:2181

if I simply pipe this like: nc -k -l 2182 | nc service 2181 I do see the response from the service on the remote-machine. So I'm able to go all the way to the service and back to the remote-machine but it stops there:

local-machine:2181 <-/- SSH --> remote-machine:2182 <-- netcat --> service:2181

so I don't understand why the named pipe won't forward the response through the ssh connection back to my local machine.

echo message | nc localhost 2182 on the remote-machine does NOT output anything back on the local-machine, so it's not making it through SSH for some reason.

Any idea why this is and how to fix it?

Thanks for help.

(EDITED for clarity) Note: I need this because I can only SSH to one machine, which is part of a cluster, and that machine has access to the service(s). I do not want to expose the service to the outside, nor have SSHD one every service container.

1

I was pointed to the fact that one can simply do

ssh -L 2181:service:2181 user@remote-machine

to forward the connection to service from remote-machine to the port on local-machine.

simple and efficient.

0

You can use -R for this purpose:

ssh -R 8080:127.0.0.1:7070 yourhost

This will open a port on yourhost:7070 that forwards to localhost:8080

Documentation says

[-R [bind_address:]port:host:hostport]

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.