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Hello forum,
i am using a Raspberry Pi (with Codesys 3.5.16.0) as a TCP IP server and almost 80 Raspberry Pi (with Codesys 3.5.16.0) as TCP IP clients. I make an Array of 80 NBS.Connections and let the clients make connections. The server allocates one element of the aforesaid Array randomly. The whole communication is working.
i have following questions:
1. The client makes connection then on server side the Server/NBS.connection.Active[x] goes true but it stays true even if the client goes physically offline. Is it so or i made an error? right now i send the timestamp from client to server and as long as it is changing, i know the connection is ok, else i reconnect. Is there any elegent way to solve this.
2. Can i decide from server side that Server/NBS.connection.Active[x] is only for Client IP xxx.xxx.xxx.xxx
3. How can i decide from client side that the server Offline is?
any help is appreciated!
Thanks in advance
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Probably the easiest approach to this is to implement a heartbeat.
Server sends client a dummy message (e.g. "HI") every X seconds to keep connection alive (when you are not regularly sending data to client).
Client also sends server a dummy message (e.g. "HI") every X seconds to keep connection alive (when you are not regularly sending data to server).
If either side does not receive this dummy message within Y intervals of X seconds, then close connection.
In each client/server function block, have a boolean input called hearbeat_check from an external timer TON that runs every X+1 seconds... or have a dedicated TON for each function block, but that would be a waste of space. Anyway, for each function block have two bytes: one called current and the other called missed_heartbeat. This variable current is set to 1 if TCP receive buffer has new message. On the rising edge of hearbeat_check, increment missed_heartbeat if current is equal to 0. Else, reset missed_heartbeat to 0. If missed_heartbeat exceeds some Y value, then close connection.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hello forum,
i am using a Raspberry Pi (with Codesys 3.5.16.0) as a TCP IP server and almost 80 Raspberry Pi (with Codesys 3.5.16.0) as TCP IP clients. I make an Array of 80 NBS.Connections and let the clients make connections. The server allocates one element of the aforesaid Array randomly. The whole communication is working.
i have following questions:
1. The client makes connection then on server side the Server/NBS.connection.Active[x] goes true but it stays true even if the client goes physically offline. Is it so or i made an error? right now i send the timestamp from client to server and as long as it is changing, i know the connection is ok, else i reconnect. Is there any elegent way to solve this.
2. Can i decide from server side that Server/NBS.connection.Active[x] is only for Client IP xxx.xxx.xxx.xxx
3. How can i decide from client side that the server Offline is?
any help is appreciated!
Thanks in advance
Probably the easiest approach to this is to implement a heartbeat.
In each client/server function block, have a boolean input called hearbeat_check from an external timer TON that runs every X+1 seconds... or have a dedicated TON for each function block, but that would be a waste of space. Anyway, for each function block have two bytes: one called current and the other called missed_heartbeat. This variable current is set to 1 if TCP receive buffer has new message. On the rising edge of hearbeat_check, increment missed_heartbeat if current is equal to 0. Else, reset missed_heartbeat to 0. If missed_heartbeat exceeds some Y value, then close connection.