TeamViewer is designed to connect easily to remote computers without any special firewall configurations being necessary. In the vast majority of cases, TeamViewer will always work if surfing on the internet is possible. TeamViewer makes outbound connections to the internet, which are usually not blocked by firewalls.
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 to connect out through it.
TCP/UDP Port 5938
TeamViewer prefers to make outbound TCP and UDP connections over port 5938 – this is the primary port it uses, and TeamViewer performs best using this port. Your firewall should allow this at a minimum.
The following ports are notused by TeamViewer running on Android, Windows Mobile, or BlackBerry:
TCP Port 443
If TeamViewer can’t connect over port 5938, it will next try to connect over TCPport 443. However, the connection speed using this port may not be quite as optimal as using port 5938.
Note: port 443 is also used by our custom modules which are created in the Management Console. If you’re deploying a custom module, eg. through Group Policy, then you need to ensure that port 443 is open on the computers to which you’re deploying.
TCP Port 80
If TeamViewer can’t connect over port 5938 or 443, then it will try on TCPport 80. The connection speed over these ports is also not as optimal as port 5938.
Android, Windows Mobile, and BlackBerry
Our mobile apps running on Android, Windows Mobile, and BlackBerry, can only connect out over port 5938. If the TeamViewer app on your mobile device won’t connect and tells you to “check your internet connection”, it’s probably because this port is being blocked by your mobile data provider or your WiFi firewall.
Destination IP addresses
The TeamViewer software makes connections to our masterservers and routers located around the world. These servers use many different ranges of IP addresses, which are also frequently changing. As such, we are unable to provide a list of our server IPs. However, all of our IP addresses have PTR records that resolve to *.teamviewer.com. You can use this to restrict the destination IP addresses that you allow through your firewall or proxy server.