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--- communication_between_2_webhmis_via_internet [2021/02/12 14:53] – ↷ Links adapted because of a move operation atolstov
+++ level2:communication_between_2_webhmis_via_internet [2022/02/08 14:07] – [Option 2. VPN and Modbus TCP] emozolyak
@@ Line 1: / Line 1: @@
-====== Communication between 2 WebHMIs via internet ======
+====== Communication between 2 or more WebHMIs via internet ======
 Sometimes you need to have a connection between far systems, e.g. like in the following picture:
-{{ ::two_webhmi_over_l2.png?direct&600 |}}
+{{ network:two_webhmi_over_l2.png?direct&600 |}}
 You might want to automatically control supply pumps depending on the water level in a far water tower or reservoir.
 With the WebHMI and Level2 connectivity options it is done with ease:
+==== Option 1. Using MQTT protocol ====
+  - Connect both WebHMIs to the Level2 IoT
+  - Subscribe the pump station WebHMI to the topic with level that far WebhMI publish onto the Level2 MQTT broker.
+==== Option 2. VPN and Modbus TCP =====
   -[[level2:how_to_connect_webhmi_to_level2|Connect both WebHMIs to Level2]] and and remember remote node (reservoir side) IP address in the VPN network
-  -Turn On ([[modbus_tcp_server|Modbus TCP Server]]) on the water redervoir side
+  -Turn On ([[:modbus_tcp_server|Modbus TCP Server]]) on the water redervoir side
-  -Enable [[remote_service_access|routing]] for pump side WebHMI to the remote peer node
+  -Enable [[:remote_service_access|routing]] for pump side WebHMI to the remote peer node
   -Create Modbus TCP connection on the pump side WebHMI using IP address from (1)
+<WRAP center round tip 60%>
+__Option 1__ Is preffered due to the nature of the MQTT protcol which saves traffice for communication while Modbus TCP will create constatn polling process.
+</WRAP>