Port 5938 TCP UDP
TeamViewer remote desktop and access protocol
TeamViewer is a tool used to gain access easily to a remote computer without any special kind of network or firewall configuration required, only the TeamViewer client installed at either site.
The machine you're trying to access will first try to connect to the TeamViewer servers via an outbound connection on port 5938, as the connection is outbound it does not require any inbound firewall rules.
In some cases, this port may be blocked, so the protocol will fall back to using the HTTPs port (TCP/443) or finally the HTTP port (TCP/80), typically these are always opened so that clients can get access to internet based web servers.
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