I use node.js with the NET class to connect multiple Rasperry Pi's.
//Server
const net = require('node:net');
const server = net.createServer();
//Client
const tcpConnect = net.createConnection(SERVERINFO);Thereby I can easily register multiple clients, open/close streams. Everything works without any problems.
But now I noticed that the callbacks.
tcpConnect.on('end', () => { console.log('end triggered') });
tcpConnect.on('close', () => { console.log('close triggered') });
tcpConnect.on('error', () => { console.log('error triggered') });do not work if the server suddenly has a power failure (e.g. power supply is pulled). The clients don't trigger an error/end or close, so I can't close the connection properly. As a result, an error is not triggered until the next attempt to write something to an existing stream. But this is not an option for me, especially for "online monitoring".
Does anyone know a way to identify the shut off of the server immediately?
You need to enable TCP keep-alives in order for the client to detect that the server is no longer responding and you can tune how often it checks on an idle connection. (I've written a language generic description at the beginning of this answer.)
In node it appears you can do this: socket.setKeepAlive(true), i.e. for this client to detect the server is gone when the socket is idle:
//Client
const tcpConnect = net.createConnection(SERVERINFO);
tcpConnect.setKeepAlive(true);