Node net data merge when multiple write - node.js

Question

I am using Node net.
When the client multiple writes feeds, and on the server-side, it received 1 data.
var net = require('net');
// SERVER SIDE
var net_port = 8080; // node net port
var server = net.createServer(function(connection){
connection.on('data', function(data){
var str = data.toString();
console.log("Received, Length: "+str.length); // IT SHOULD be 25 in length
});
connection.pipe(connection);
});
server.listen(net_port, function() {
console.log('server is listening');
});
// SERVER CODE NED
// ### CLIENT SIDE
var client = net.connect({port: 8080}, function() {
console.log('connected to server!');
});
string = "acdefghijklmnopqrstuvwxyz"; // 25 char
setInterval(function(){
client.write(string);
client.write(string);
},1);
setInterval(function(){
client.write(string);
client.write(string);
},1);
Sending string with length 25, but when received OUTPUT IS
Received, Length: 25
Received, Length: 25
Received, Length: 75 // merged 3 data
Received, Length: 100 // merged 4 data
Received, Length: 25
Received, Length: 50 // merge 2 times
Received, Length: 75
Received, Length: 25
Received, Length: 25
Received, Length: 25
Received, Length: 100
IN reality, in my actual code, I cant use split string, because if a client sends String length 100 4 times. so server received
Received, Length: 100
Received, Length: 220
Received, Length: 80
How I can force Node Net to send and received actual data.
Fiddle: https://www.mycompiler.io/view/BJGjA87

Answer 1

net.createServer creates a TCP server. TCP sockets are stream-based, not datagram-based. They don’t have a concept of message boundaries: everything is just a one contiguous stream of bytes with no markers distinguishing which fragments were sent together and which separately. If you want to establish boundaries between messages sent over a TCP socket, you have to delineate them yourself: either by postulating that each message must have a fixed length in bytes, or by introducing markers that establish where one message ends and another starts.
Below, as an example, is a simple modification of your server that uses the json-seq format defined in RFC 7464 to that end. More long-term, you may look into making it a WebSocket server instead, using a library such as ws. It would probably be more robust than the code below; this is mostly just a demonstration.
var net = require('net');
var server = net.createServer(function (connection) {
var buffer = '';
function receivedMessage(value) {
console.log('received: ' + JSON.stringify(value));
}
function protocolError() {
console.log('protocol error');
connection.close();
}
function parseMessages(buf) {
console.log('parsing ' + buf.length + ' code units worth of messages');
if (buf.substring(0, 1) !== '\x1e') {
protocolError();
return;
}
var m, rx = /\x1e([^\x1e]*)/g;
while (m = rx.exec(buffer)) {
if (m[1] === '')
continue;
try {
var value = JSON.parse(m[1]);
} catch (e) {
if (e instanceof SyntaxError)
continue; // RFC 7464 §2.3
throw e;
}
receivedMessage(value);
}
}
connection.on('data', function (data) {
buffer += data.toString('utf8');
console.log(buffer.length + ' code units in the buffer');
var lastRS = buffer.lastIndexOf('\x1e');
if (lastRS === 0)
return;
var fullMessages = buffer.substring(0, lastRS);
buffer = buffer.substring(lastRS, buffer.length);
parseMessages(fullMessages);
try {
var value = JSON.parse(buffer);
} catch (e) {
if (e instanceof SyntaxError)
return; // maybe just truncated; defer error until later
throw e;
}
receivedMessage(value);
buffer = '';
});
connection.on('close', function () {
console.log('closed');
parseMessages(buffer);
});
});
server.listen(8080, function() {
console.log('server is listening');
});
And here’s an appropriately-modified client:
var net = require('net');
var client = net.connect({port: 8080}, function() {
console.log('connected to server!');
});
function sendMessage(value) {
client.write(Buffer.from('\x1e' + JSON.stringify(value) + '\n', 'utf8'));
}
string = 'acdefghijklmnopqrstuvwxyz';
setInterval(function(){
sendMessage(string);
sendMessage(string);
}, 1);
setInterval(function(){
sendMessage(string);
sendMessage(string);
}, 1);