A new class governs the receiving and sending of messages.
In each message there’s a variable called ack. Its value is false when it’s a normal message.
However upon receiving a message an empty message with the unique message_id will be sent
with ack = true.
Upon receiving this ack, the peer will be removed from the resend list. However when a message needs
to be resent, it is assumed that the peer is not connected with the sender. The peer will then be added
as a neighbor and the message will be resent.