If TeamViewer (Classic) can’t connect over port 5938 or 443, then it will try on TCP port 80. Port 443 is also used for a few other things, including TeamViewer (Classic) update checks.

through Group Policy, then you need to ensure that port 443 is open on the computers to which you’re deploying. 📌Note: port 443 is also used by our custom modules which are created in the Management Console.

However, our mobile apps running on iOS and Windows Mobile don't use port 443. If TeamViewer (Classic) can’t connect over port 5938, it will next try to connect over TCP port 443. Your firewall should allow this at a minimum. TeamViewer (Classic) prefers to make outbound TCP and UDP connections over port 5938 – this is the primary port it uses, and TeamViewer (Classic) performs best using this port. These are the ports that TeamViewer (Classic) needs to use. However, in some situations, for example in a corporate environment with strict security policies, a firewall might be set up to block all unknown outbound connections, and in this case, you will need to configure the firewall to allow TeamViewer (Classic) to connect out through it. TeamViewer (Classic) makes outbound connections to the internet, which are usually not blocked by firewalls.

In the vast majority of cases, TeamViewer (Classic) will always work if surfing on the internet is possible. TeamViewer (Classic) is designed to connect easily to remote computers without any special firewall configurations being necessary. This article applies to all users in all licenses.

Team viewer uses