I have a server with defined IP address (it is for my own usage). I would like to use it from remote access. The server is behind a firewall. Is there a way to access it from remote computer? Is TeamViewer going to do the work? Is there any other solution without a need to open a port?

I would like to mention that in both the server and the remote computer the OS is Windows. In the server Windows for server and in the remote computer Windows 8.

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    That depends entirely on the configuration of the firewall, what kind of communication it allows and what kind it prevents. – Philipp Dec 26 '15 at 17:57
  • Thanks a lot @Philipp. If I don't know the configuration of the firewall is there still a way to remote access. Would reverse ssh work in every configuration? – Avi Dec 26 '15 at 18:01
  • maybe, maybe not. It depends on the firewall configuration. When you can not provide any information at all about the firewall, we can not help you with it. – Philipp Dec 26 '15 at 18:23
  • Is there a way to find the firewall configuration from remote? and is there a procedure to use reverse ssh in Windows OS? – Avi Dec 26 '15 at 18:32

There are several possible solutions. TeamViewer will work because its basicly whats called a "backconnect". This means that TeamViewer from the view of the firewall acts as a client, not as a server by initializing the connection instead of waiting for the incoming connection like a server does. This way TeamViewer bypasses statefull firewalls.

If you want to you can also use a port forwarding. This means that you configure your firewall to foreward all incoming traffic from external hosts on a specific port to another host on the LAN. This is called PAT (Port Address Translation) and is widely used. How this can be implemented relies on your router but almost every routers support this. You can also expand this solution with portknocking which is a "security through obscurity" kind of approach. It means that a connection is only accepted after a defined packet has been received before from the same source.

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  • Thanks a lot @davidb. If I have no access to the firewall. I have access as administrator to my server (behind the firewall) and to my home computer is there any additional solution to TeamViewer? – Avi Dec 26 '15 at 19:03
  • TeamViewer hast a kind of monopolistic position but you can implement other solutions if you are a skilled programmer and have a good understanding of networking – davidb Dec 26 '15 at 19:08
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    It's not true that TeamViewer will always work. If a firewall is configured to block outgoing connections, you're out of luck. – Jeroen Dec 26 '15 at 19:58
  • Yes of cause if the firewall uses whitelisting and the used port isn't whitelisted it won't work... – davidb Dec 26 '15 at 20:02

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