SSH Remote Port Forwarding Empty Response

Question

I am trying to Remote port forward from Raspberry pi in my local network using ssh on my windows pc

ssh -R 5941:localhost:8000 [email protected]

So from the above command, I am trying to forward connections from port 5941 on Raspberry pi server (192.168.1.191) to port 8000 on my pc (localhost) which hosts a web server on port 8000

The above ssh command executes with no errors but when i try to access http://localhost:5941/ on Raspberry Pi (192.168.1.191) i get

ERR_EMPTY_RESPONSE

I have tried

Turned off firewall on my Windows PC
netstat on raspberrypi gives me

$ sudo netstat -a | grep 5941
tcp        0      0 0.0.0.0:5941        0.0.0.0:*               LISTEN
tcp6       0      0 [::]:5941               [::]:*                  LISTEN

when i run the ssh command in verbose mode ssh -R 5941:localhost:8000 [email protected] -v I get this

debug1: Remote connections from LOCALHOST:5941 forwarded to local address localhost:8000
debug1: channel 0: new [client-session]
debug1: Requesting [email protected]
debug1: Entering interactive session.
debug1: pledge: network
debug1: console supports the ansi parsing
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug1: Remote: Forwarding listen address "localhost" overridden by server GatewayPorts
debug1: remote forward success for: listen 5941, connect localhost:8000
debug1: All remote forwarding requests processed

and when i try to access http://localhost:5941/ on Raspberry Pi (192.168.1.191) i get this on ssh console

debug1: client_input_channel_open: ctype forwarded-tcpip rchan 3 win 2097152 max 32768
debug1: client_request_forwarded_tcpip: listen localhost port 5941, originator ::1 port 58122
debug1: getsockopt TCP_NODELAY: Invalid argument
debug1: connect_next: host localhost ([::1]:8000) in progress, fd=7
debug1: channel 1: new [::1]
debug1: confirm forwarded-tcpip
debug1: channel 1: connected to localhost port 8000
debug1: channel 1: free: ::1, nchannels 2

How should I further diagnose my problem ?

What service is running on localhost:8000 on the local system? Is the process which provides this service logging any messages? — Kenster
– Kenster, Commented Apr 21, 2021 at 18:36

Aun Rizvi · Accepted Answer · 2021-04-21 20:40:06Z

19

The solution to this is to put 127.0.0.1 instead of localhost

ssh -R 5941:127.0.0.1:8000 [email protected]

This forces ipv4 instead of ipv6, for some reason ssh port forwarding in windows fails to work on ipv6, I was able to work the same command with localhost on linux just fine.

I found the solution from this post here

answered Apr 21, 2021 at 20:40

Aun Rizvi

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3 Comments

ryan Over a year ago

For other's who may land here, I made the change above (i.e. 127.0.0.1 instead of "localhost") into a "gcloud compute ssh .." port forwarding command into a GCP windows server VM and my ZMQ REQ/REP python connection suddenly came alive.

Said Torres Over a year ago

Don't forget to enable: AllowTcpForwarding yes and GatewayPorts yes in /etc/ssh/sshd_config and restart the SSH service after changes: sudo systemctl restart sshd

Nikola Petrovic Over a year ago

Thanks. This was the solution. Very weird and inconsistent with Linux implementations

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