You are behind a firewall (that allows only port 80 or 443), and therefore cannot access a remote Unix machine via ssh (port 22).
Change the port on which ssh runs on Linux Server:
Run the ssh on the Unix machine on port 443.
In dir: /etc/ssh dir locate following files: ssh_config, sshd_config (do we need to do for both files or only sshd_c0nfig?)
Here uncomment the line: #Port 22 , and change port number to 443.
Now restart ssh: /etc/init.d/sshd restart
Now ssh on the Linux server is running on port 443 (instead of default 22)
Next, ssh using Putty from your desktop
- Under Session> Enter Server IP and Port (remember 443, and not 22).
- If a Proxy Server is in place (its likely if you are behind a firewall) then, under Connection > Proxy enter the Proxy Details. Often people forget this step. If Proxy requires Authentication enter user (eg: email@example.com) and passwd for that.
- If you need to enter any Private Auth Key file (usually the case if you are accessing say Amazon EC2) do that under SSH> Auth.
Now hit Open. Hopefully everything will work out fine.
If you often get disconnected in a ssh session, becz you were idle, you must enter a value in Connections> Seconds between Keep Alives.
Note: Always follow the applicable procedures and laws of your place. Do not circumvent firewalls, if you are not allowed to.