Wait/reconnect until TCP client connection can be established? - node.js

Question

Here is an example of how to create a TCP client connection from the node net docs (https://nodejs.org/api/net.html#net_net_connect_options_connectlistener)
const client = net.createConnection({ port: 1905 }, () => {
// 'connect' listener
console.log('connected to server!');
client.write('world!\r\n');
});
client.on('data', (data) => {
console.log(data.toString());
client.end();
});
client.on('end', () => {
console.log('disconnected from server');
});
If the server is not available I get Error: connect ECONNREFUSED 127.0.0.1:1905.
What would be a good way to wait/reconnect until the server is available and connect when it is, instead of throwing an error?
EDIT: Here is an alternative approach I have tried, but here I get the problem
MaxListenersExceededWarning: Possible EventEmitter memory leak
detected. 11 connect listeners added. Use emitter.setMaxListeners() to
increase limit
I would like the latest listener to replace earlier listeners. They all listen for the same thing. I just want to retry.
function initTcpClient() {
console.log("Initiating TCP client...")
var tcpSocket = new net.Socket();
const client = net.createConnection({ port: 1905 }, () => {
tcpSocket.on('error', function onError(err) {
setTimeout(connect, 1000);
});
connect();
function connect() {
console.log("Looking for TCP server...");
tcpSocket.connect(argv.tcpport, argv.tcphost, function onConnected() {
console.log("Connecting to TCP server...");
tcpSocket.on('data', function onIncoming(data) {
if (connectedWebsocketClient) {
console.log('Forwarding to WebSocket: %s', data);
webSocketClient.send(data.toString());
} else {
console.log('Not connected to websocket client. Dropping incoming TCP message: %s', data);
}
});
tcpSocket.on('close', function onClose(hadError) {
console.log("Connection to TCP server was closed.");
connectedToTcpServer = false;
setTimeout(connect, 1000);
});
console.log("Connected to TCP server.");
connectedToTcpServer = true;
});
}
}

Answer 1

Here to elaborate on my comment. Is an example that will work. Try it with a simple tcp server. Start the client and then after a few seconds start the server. It is important to register you listeners after a reconnect happens in onError You may also want to have a limit of how many times you want to try to reconnect.
const net = require('net')
let client = connect()
client.on('data', onData);
client.on('error', onError);
client.on("close", onClose);
function onData(data) {
console.log(data)
}
function onError(err) {
if(err.message.indexOf('ECONNREFUSED') > -1) {
//do recconect
console.log("Attempting to reconnect shortly")
setTimeout(()=>{
client = connect();
client.on('data', onData);
client.on('error', onError);
client.on("close", onClose);
},1000)
}
}
function onClose() {
console.log("Removng all listeners")
client.removeAllListeners("data");
client.removeAllListeners("error")
}
function connect() {
const c = net.createConnection({
port: 3000
},
()=>{
console.log('connected')
});
return c
}