new feature: support network node that need to deal with heart beat or keep alive on the same socket

Currently the network node are bound with a certain protocol, this prohibits the usage of
rammbock from end/terminal that equipped with alive detection mechanism.
Since alive detection packet normally are not compatible with interaction protocol on the same socket,
we need to do some ugly hacking in _receive_msg_ip_port function in _NetworkNode class in order to involving rammbock in that kinds of scenario.
I come from Nokia, and our team hopes that our test cases can keep synchronized with robot and rammbock update.

Start by reading the _NetworkNode class and its _receive_msg_ip_port function to understand how protocol-bound socket messages are received. Define how heartbeat or keep-alive packets can coexist with the interaction protocol on one socket, then verify that Rammbock can support the described terminal scenarios without disrupting existing network behavior.

Written by the indexing model from the issue text.