Connection is not closed when exiting Unity play mode

[brean]

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The connection is kept open and it still sends and receives data from the server after you exit the play mode (at least on the dev-branch you can still see the ping-pong messages in the console log). This might be expected behaviour when you start the communication from the Inspector but might be inconvenient in most cases when you connect during program runtime. Close should maybe be called when the object gets destroyed.