Specify network interface (WAN) to use
(Everything below applies to Windows 10, have no idea about the other supported platforms)
Currently TeamViewer Windows client seems to select the network interface it uses based on some internal heuristic, which fails when the machine has more than one IPv4 interface configured.
Sometimes TeamViewer chooses to use an interface that doesn't have WAN/internet connectivity and just indefinitely tries to connect, without realizing that it's just not going to work.
Preferably, instead of seemingly "blindly" choosing the interface, TeamViewer should let the user to configure the preferred adapter to use in the settings.
Auto-detection could still be the default (to retain current behavior), but it should be bit more smart; If it cannot connect using interface X within say 30s, then move on to next compatible (whatever that criteria for compatible is) interface and try that. If all compatible interfaces fail, only then give up and inform the user.
(A simple strategy for detecting the default connection using single UDP datagram is here: https://stackoverflow.com/questions/24661022/getting-ip-adress-associated-to-real-hardware-ethernet-controller-in-windows-c/24664853#24664853)