https://forge.codesys.com/forge/talk/Engineering/thread/d24dd8f315/2020-09-18T06:59:13.911000ZRecent posts to TCP/IP Connection monitoring based on Network 3.5.7.0 Library2020-09-18T06:59:13.911000Z2020-09-18T06:59:13.911000Znothinrandomhttps://forge.codesys.com/u/nothinrandom/https://forge.codesys.com5dbaf257f698dc523836397bb3cad1a0480ac705

<div class="markdown_content"><p>Probably the easiest approach to this is to implement a heartbeat. </p> <ul> <li>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).</li> <li>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).</li> <li>If either side does not receive this dummy message within Y intervals of X seconds, then close connection.</li> </ul> <p>In each client/server function block, have a boolean input called <strong>hearbeat_check</strong> 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 <strong>current</strong> and the other called <strong>missed_heartbeat</strong>. This variable <strong>current</strong> is set to <strong>1</strong> if TCP receive buffer has new message. On the rising edge of <strong>hearbeat_check</strong>, increment <strong>missed_heartbeat</strong> if <strong>current</strong> is equal to <strong>0</strong>. Else, reset <strong>missed_heartbeat</strong> to <strong>0</strong>. If <strong>missed_heartbeat</strong> exceeds some Y value, then close connection.</p></div>

2020-09-04T10:33:38.541000Z2020-09-04T10:33:38.541000Zbaldeephttps://forge.codesys.com/u/baldeep/https://forge.codesys.comf7ed25c3180b6555f5809daa3254bf40c407f79c

<div class="markdown_content"><p>Hello forum,<br/> 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.</p> <p>i have following questions:<br/> 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.<br/> 2. Can i decide from server side that Server/NBS.connection.Active[x] is only for Client IP xxx.xxx.xxx.xxx<br/> 3. How can i decide from client side that the server Offline is?</p> <p>any help is appreciated!<br/> Thanks in advance</p></div>