Prevent people from connecting from same port

[evonneng]

Currently if people are training on the same port, you end up seeing the same thing. Ideally you would have some way (e.g. send a key or something) to make sure that is the intended connection point. Otherwise, prompt them to enter in new port.

[evonneng]

Looking into using redis perhaps to keep state? but maybe overkill..

[tancik]

Warning now provided to user