nodejs tls module for server-client communication without browser - node.js

Question

I wish to securely send messages back and forth between a client and a remote server (just an IP address and a port) using nodejs. The client runs a local .js file and does not use a browser. I have tried to do so using the node TLS module (https://nodejs.org/api/tls.html).
The handshake works perfectly fine, but I can not manage to send a message from the server to the client. My current code is:
client.js
const tls = require('tls');
const fs = require('fs');
const options = {
host: <server IP address>,
port: <port number>,
key: fs.readFileSync('client.key'),
cert: fs.readFileSync('client.crt'),
ca: fs.readFileSync('ca.crt'),
checkServerIdentity: function (host, cert) {
return undefined;
}
};
const client = tls.connect(options, function(){
if (client.authorized) {
console.log("Connection authorized");
} else {
console.log("Connection not authorized: " + conn.authorizationError)
}
process.stdin.pipe(client);
process.stdin.resume();
client.emit('data','message')
});
client.setEncoding('utf8');
client.addListener('data', function(data) {
console.log(data);
});
client.on('end', () => {
server.close();
});
server.js
const tls = require('tls');
const fs = require('fs');
const options = {
key: fs.readFileSync('server.key'),
cert: fs.readFileSync('server.crt'),
ca: fs.readFileSync('ca.crt'),
requestCert: true,
rejectUnauthorized: true
};
const server = tls.createServer(options, function(socket){
console.log('server connected',
socket.authorized ? 'authorized' : 'unauthorized');
socket.setEncoding('utf8');
socket.pipe(socket);
socket.emit('data','I am the server')
});
server.listen(<port number>,function(){
console.log('listening')
})
server.on('connection',function(client){
console.log('client connected')
client.on('data',function(data){
console.log(data)
})
})
The server does output 'client connected' but does not do anything with the client.on() part, and I can not find another way to make the server listen for messages from the client. Is there a way to use the tls module so that I can make the client and server interact based on the messages they send and receive? Again, I do not want to use a browser.

Answer 1

The comments by #robertklep helped me solve my issue. Delete the socket.pipe(socket) line on the server side, and on the client side just use socket.write() to send a message to the server. This can be received by a socket.on('data') instance on the server side. Also, to interact with multiple clients, you can write something like:
var socket = {};
const server = tls.createServer(options, function(s){
client=s.getPeerCertificate().subject.CN
socket[client] = s;
socket[client].setEncoding('utf8');
socket[client].write('welcome')
for (key in socket){
socket[key].write('new client connected')
}
socket[client].on('data',function(data){
socket[client].write('data received')
})

Answer 2

I think using a Set for notifying new connections of being connected makes more sense. An object being added to a set must be unique to the set if it is to be added. You can also just use socket.server._connectionKey to determine what client it is, don't have to mess around with getting the peer certificate.
var sockets = new Set();
const server = tls.createServer(options, (socket) => {
console.log('server connected',
socket.authorized ? 'authorized' : 'unauthorized');
var sock_set_len = sockets.size; //get size of sockets set
var key = socket.server._connectionKey;
sockets.add(key); //attempt to add socket to connection list
if(sock_set_len < sockets.size) { //if the socket _connectionKey is unique, it will be added, and will be treated as a new connection here.
socket.write("you are connected...");
}
socket.on('data',function(data){
socket.write(data);
})
socket.on('end', socket.end);
});
On a side note, I created a package to handle sockets with Obj-C iOS, taking into account the latest (iOS 13) TLS restrictions imposed by Apple:
https://github.com/eamonwhiter73/IOSObjCWebSockets
I used a Node JS TLS server to receive connections, a variation of the echo server example in the Node JS docs