Ubuntu – ssh as socks proxy – channel 5: open failed: connect failed: Connection refused

Once you can connect to the machine from inside your LAN, the rest is completely outside of the control of Ubuntu running on that machine. So the problem is likely to be somewhere outside of your Ubuntu box. Possible causes may include:

• incorrectly configured port forwarding on your router. Note that the internal IP of your machine may change when you reboot it, especially if you have more than one device in your LAN, it may depend on the order addresses are requested from the router's DHCP. You can use ifconfig command in the console to see your IP address.

• you using an incorrect IP when trying to connect from outside (actually, "No route to host" message strongly suggests that). Google "what is my ip" to find one of many sites which will tell you what your current external IP is. Note your external IP may change if you reboot the router.

• As a "security measure", some providers block incoming connections to their client's ports - either all ports or a range of well-known ports. There may be some setting in the ISP's control panel or you may need to call them to figure this out.

So the way to debug the problem would be:

• make sure you can connect from within LAN
• make sure you correctly configured port forwarding on the router using the correct internal IP of your machine
• figure out your external IP
• make sure you can ping that IP, use traceroute to see where the packets are blocked
• possibly try configuring forwarding for some "easier" service, such as HTTP first to exclude problems with authentication etc.

(also, I'm not sure why you're mentioning DNS stuff - everything is done via plain IP addresses, DNS has absolutely nothing to do with it)

You would do a lot better to "forward" the remote network's proxy server over SSH rather than using the built-in SOCKS server (which just expects a bare gateway-addressable network at the other end).

ssh -L 8080:internal_ip_of_proxy:8080 user@ssh_server

This exposes the proxy server locally, allowing you to set your browser's proxy settings to localhost:8080 and that will tunnel over SSH to the remote proxy.

And you can apply this to any remote service. You could, for example, tunnel Imgur from your server (in effect a single-host proxy):

ssh -L 8080:imgur.com:80 user@ssh_host

And on a local terminal:

curl --header 'Host: imgur.com' localhost:8080

The Host header is required otherwise curl will request a non-existent localhost site. You could also work around that by adding a line in /etc/hosts, resolving imgur.com to 127.0.0.1... But I'm getting off-topic, you don't need any of this for your purposes.