Port Forward Directly to a Guest OS with VirtualBox

Question

Hi all,

I am currently using Ubuntu 10.04 for some rails development. It is installed as a guest machine using VirtualBox on a Windows 7 x64 host.

Within Ubuntu, I am trying to port tunnel several ports from a remote server directly to the Guest OS in order to avoid having to download a remote database.

Let's say I want to forward port 5000 on the remote server to port 5000 on the guest os.

I have set up a forwarder for the port on the Windows side, using VBoxManage.exe. This forwards HostPort 5000 to GuestPort 5000.

Then within ubuntu I run, ssh -L5000:127.0.0.1:5000. However, whenever I try to access "127.0.0.1:5000", I receive the message "channel 7: open failed: connect failed: Connection refused"

Am I missing something?

Thanks for the help!

Answer 1

connect failed: Connection refused

This means that you'r not able to connect to 5000 on the remote end.

If you'r only using this connection from within your guest through your SSH tunnel then you don't need the forward from VBoxManager, as this will open op so that outside computers can connect directly to your guest, it won't help your guest connect to the outside.

Are you sure the server you connect (SSH) to is the same server that runs your database? And is the database running on that server?

When you've connected (SSH) to the server, you can try to list what ports are listening for connections or you could try to connect to the database with telnet. To list listeners you can run "netstat -lnt" (-l shows listening, -n is numeric (show IP and port number) and -t is tcp). You should have a line like "tcp 0 0 0.0.0.0:5000 0.0.0.0:* LISTEN" if you have a service listening for TCP on port 5000. To try and connect you can simply do "telnet 127.0.0.1 5000", if you can't connect with telnet from the server then the database ain't listening/allowing your connection, or the server is running on another port or server.

Answer 2

SSH uses TCP traffic by default, right?

Just to verify, NAT in VirtualBox does have these limitations (per the User Manual):

There are four limitations of NAT mode which users should be aware of:

ICMP protocol limitations: Some frequently used network debugging tools (e.g. ping or tracerouting) rely on the ICMP protocol for sending/receiving messages. While ICMP support has been improved with VirtualBox 2.1 (ping should now work), some other tools may not work reliably.

Receiving of UDP broadcasts is not reliable: The guest does not reliably receive broadcasts, since, in order to save resources, it only listens for a certain amount of time after the guest has sent UDP data on a particular port. As a consequence, NetBios name resolution based on broadcasts does not always work (but WINS always works). As a workaround, you can use the numeric IP of the desired server in the \server\share notation.

Protocols such as GRE are unsupported: Protocols other than TCP and UDP are not supported. This means some VPN products (e.g. PPTP from Microsoft) cannot be used. There are other VPN products which use simply TCP and UDP.

Forwarding host ports lower than 1024 impossible: On Unix-based hosts (e.g. Linux, Solaris, Mac OS X) it is not possible to bind to ports below 1024 from applications that are not run by root. As a result, if you try to configure such a port forwarding, the VM will refuse to start.