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When devices are connected under multiple levels of NATs (or routers), the devices under upper levels cannot reach the devices under the lower ones directly even if they know the IP address (Network limitation). With the Multi-NAT Edge Device Communications (MNEDC) system, the devices can communicate with each other once they establish a persistent connection with MNEDC server which is running on topmost level of NAT, acting as a relay between devices and helping in communication by providing a channel.
MNEDC Server
This is a TCP server running on any one of the devices which is reachable from all other IoT devices in the network. Since Sub NAT devices can reach Main NAT device and the other way round is not possible, we need to run the MNEDC server in the Main NAT. This MNEDC Server registers the client whenever the request comes and establishes a persistent connection. Also, it provides it with a unique virtual IP in the address space of 10.0.0.1~255. Then it maintains a key-value map of the unique virtual IP and the TCP connection object. Now the role of server is to get the packets from clients, extract the target virtual IP, and write the packets on the TCP connection object which is retrieved from the map. In this way a device anywhere in the network can communicate with all the devices irrespective of their position in network.
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