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From the author of Troubleshooting

Troubleshooting

If you cannot see the Apache test page, try opening http://www.google.com or any other website that you know is accessible in the browser. If there is a problem with the tunnel, you should see a message from Firefox, as shown in Figure 6. If the website is visible, the problem is somewhere else.

Figure 6 Browser message displayed due to a proxy problem.

If the problem is somewhere else than the tunnel, try opening port 80 in the firewall to the web server, to see if it can be reached directly. You can do that with the following command:

$ sudo /sbin/iptables -A INPUT -p tcp --dport 80 -j ACCEPT

You should also check the event messages in the PuTTY client. You can find the location of the event log from the PuTTY menu, as shown in Figure 7.

Figure 7 SSH event log.

If the PuTTY event log shows an entry with connection refused resulting from your HTTP request on port 80, there may be a configuration problem with the virtual machine, or your firewall may be preventing the connection (even though it's from the local machine). Try to curl to the machine, using its IP address from the SSH console, to make sure that it's available locally. Since ICMP (ping) may be blocked, it's best in this case to use curl to troubleshoot. The following example shows this problem:

$ curl 170.225.160.64
curl: (7) couldn't connect to host

In this case, check whether the firewall is blocking the connection, using the iptables command:

$ sudo iptables -L -n -v
Chain INPUT (policy DROP 547 packets, 92420 bytes)
. . .

If so, go back and check the firewall rules in Step 2: Start PuTTY with the SOCKS Proxy Option.

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