DataSync Network

The Transmission Control Protocol (TCP) is used for point communication between terminals. TCP allows communication between two terminals through their IP addresses. TCP receives a message from the other terminal and confirms receipt of the message by sending the terminal a status of 200, but does not respond to it, as in normal HTTP.

With XMLHttpRequest, the sending terminal creates POST requests to the other terminal directly to its IP address. Requests contain the necessary action in the request body, such as getting the entity, and data for transmission to another terminal.

With the implementation of the TCP plugin, the server does not know how to wait for a response from the other side. All communication between terminals is carried out through requests only without an answer to them. The TCP server can know only if the message was delivered.

In each POST request, the identifier of the request is added, which is necessary to determine which request is received and whether to process it or respond to it.

An Example of a TCP Message

{ 
"request_id": "27c98301-9179-4a9c-8cf6-836a3686fc2f",
 "type": "request",
 "action": "resources-list",
 "data": {
   "feedType": "orderState"
   }
}

The User Datagram Protocol (UDP) is used to broadcast the terminal’s state to the entire network and to receive notification from other terminals. Sending a UDP message does not happen directly to the selected terminal, but directly to the public local network. The public local network has already received the message by each of the devices, and has raised the UDP server on the specified port.

One UDP message format is the minimum required data set of one feed to determine the difference between the local and remote feeds of two terminals, which is necessary because the size of a single UDP message should not exceed 4096KB.

The first terminal to receive a UDP message determines through the message's channel if the incoming message belongs to the site within which it operates. It is necessary that the data in one site should not be mixed with the data of another.

Unless an administrator explicitly enables multi-cast for DataSync, all terminals need to be in the same subnet.

An Example of a Broadcast UDP Message

"XPOS{
 "meta": {
   "name": "XPOS:4065",
   "sender": {
     "port": 12000,
     "address": "172.17.6.108"
   },
   "channel": "XPOS:5a7432f64b0142001677b950"
   }, 
   "payload": {
     "feed": "orderState",
     "count": 150,
     "updateTime": 1525440936663
   }
}"