I found these two links about clinet/server socket programming in NodeJS:
TCP Example &
NetJS;
So i configured my micro server like this:
const SOCKETServer = net.createServer((socket) => {
socket.write('Server is listening!\r\n');
socket.pipe(socket);
});
SOCKETServer.on('data', (data) => {
console.log('CLIENT: ' + data.toString());
});
SOCKETServer.listen(5000, '127.0.0.1');
and also my client like this:
const net = require('net');
const client = new net.Socket();
client.connect(5000, '127.0.0.1', () => {
setTimeout(sender, 1500, null);
});
client.on('data', (data) => {
console.log('SERVER: ' + data);
});
let sender = () => {
client.write('Hello Server\r\n');
setTimeout(sender, 1500, null);
};
The code works fine and i can get data from server in client. I also can send data to server from client and i can read and see its feedback in client cause of socket.pipe(socket). The problem is i cannot read anything in data event in server.
Here:
SOCKETServer.on('data', (data) => {
console.log('CLIENT: ' + data.toString());
});
net.Server doesn't have data event.
You should read from incoming socket in createServer
const SOCKETServer = net.createServer((socket) => {
socket.write('Server is listening!\r\n');
socket.on('data', function(data) {
console.log('CLIENT:', data.toString());
})
socket.pipe(socket);
});
Related
So i'm building an vscode extension in typescript and node and i have a python app which sends data with socket to localhost 8080 and im catching it like this :
export default async function getSock(port, adress, dataOld): Promise<void> {
let server = net.createServer(function (socket) {
socket.setEncoding('binary');
socket.on('data', async function (data) {
console.log('client send:' + data);
let m = port
new **UI**(data);
server.close()
});
socket.on('error', function (exception) {
console.log('socket error:' + exception);
socket.end();
});
socket.on('close', function (data) {
console.log('client close:' + data);
});
socket.on('end', function() {
console.log('disconnected from server');
server.close()
});
})
server.listen({port: port, adress: adress});
}
Now i need some mechanism that if listening for 5 seconds and no data passed from the socket, i stop listening and call "new UI(dataOld)"
First time trying TCP and made a program which returns the square of the number sent by the client.
How to ask the client for a number everytime they are idle for 'n' seconds?
I tried the setTimeout method but it triggers after those 'n' seconds have passed and then it does does not get triggered again.
Client:
const net = require('net');
const readline = require('readline').createInterface({
input: process.stdin,
output: process.stdout
});
const options = {
port : 1234
};
const client = net.createConnection(options, () => {
console.log("Connected to server")
});
client.on('data', (data) => {
console.log(data.toString());
});
client.setTimeout(2000, () => {
readline.question('Number to be squared: ',(num) => {
client.write(num);
});
});
Server:
const net = require('net');
const port = 1234;
const server = net.createServer(conn => {
console.log('New client joined');
conn.on('data', (data) => {
console.log(`Data received from client: ${data}`)
data = parseInt(data);
data = Math.pow(data,2);
conn.write('From server- '+data.toString());
});
conn.on('end',() => {
console.log('Connection stopped');
});
conn.on('error',(e) => {
console.log('Connection stopped-', e.message);
});
});
server.listen(port);
You need to listen to the timeout event, callback will be called only once. From the doc:
The optional callback parameter will be added as a one-time listener for the 'timeout' event.
socket.setTimeout(3000);//setting here.
socket.on('timeout', () => {
console.log('socket timeout');
socket.end();
});
I'm new to node, and trying to write the most minimal tcp client that sends raw hexadecimal data. if I should use a buffer then how? if I can send hex as string then how? would really appreciate guidance!
heres the current, not working code:
var hexVal = `504f5354202f6c696e653320485454502f312e310d0a557365722d4167656e743a206e6f64652d6170700d0a4163636570743a202a2f2a0d0a686f73743a203139322e3136382e31342e39343a333030300d0a636f6e74656e742d747970653a206170706c69636174696f6e2f6a736f6e0d0a636f6e74656e742d6c656e6774683a2031390d0a436f6e6e656374696f6e3a20636c6f73650d0a0d0a227b757365726e616d653a202776616c277d22` // my raw hex, unwantendly sent as string
var net = require('net');
var HOST = '192.168.14.94';
var PORT = 3000;
var client = new net.Socket();
client.connect(PORT, HOST, function() {
console.log('CONNECTED TO: ' + HOST + ':' + PORT);
client.write(hexVal);
});
client.on('data', function(data) { // 'data' is an event handler for the client socket, what the server sent
console.log('DATA: ' + data);
client.destroy(); // Close the client socket completely
});
// Add a 'close' event handler for the client socket
client.on('close', function() {
console.log('Connection closed');
});
server:
nc -lvp 3000
This solved it:
var bytesToSend = [0x50, 0x4f, ...],
hexVal = new Uint8Array(bytesToSend);
There is a more convenient way to do what you want, given a hex string send it as raw bytes.
Currently you're using a Uint8Array for which each byte needs to be encoded as 0x41 or something.
However, given a hex string, you can prepare a raw hex buffer as such:
const hexString = "41424344";
const rawHex = Buffer.from(hexString, 'hex');
And then you can write the buffer to the socket:
let client = new net.Socket();
client.connect(PORT, IP, () => {
console.log("Connected");
client.write(rawHex); //This will send the byte buffer over TCP
})
Hope this helps
you need to set server first !!!
then and only then client can connect to it ...
var net = require('net');
var config = {
host: 'localhost',
port: 3000
};
// var hexVal = `POST /line3 HTTP/1.1
// User-Agent: node-app
// Accept: */*
// host: 192.168.14.94:3000
// content-type: application/json
// content-length: 19
// Connection: close
// "{username: 'val'}"`
var hexVal = `504f5354202f6c696e653320485454502f312e310d0a557365722d4167656e743a206e6f64652d6170700d0a4163636570743a202a2f2a0d0a686f73743a203139322e3136382e31342e39343a333030300d0a636f6e74656e742d747970653a206170706c69636174696f6e2f6a736f6e0d0a636f6e74656e742d6c656e6774683a2031390d0a436f6e6e656374696f6e3a20636c6f73650d0a0d0a
227b757365726e616d653a202776616c277d22` // my raw hex, unwantendly sent as string
var move = {
forward: hexVal,
backward: 'READER_BWD'
};
///////////////////////////////////////////////////////////////////////////////////
/* server code */
let server = net.createServer((client) => {
console.log('client connected');
client.on('data', data => {
console.log(data.toString());
client.write('ACK')
})
client.on('end', () => console.log('ended session'))
})
server.listen(3000)
//////////////////////////////////////////////////////////////////////////////
/* client code */
var client = new net.Socket();
client.connect(3000, 'localhost', function () {
console.log('connected to ' + config.host + ':' + config.port);
client.write(move.forward, function () {
console.log('move forward command sent');
});
});
client.on('data', function (data) {
var str = data.toString();
if (str === 'ACK') {
console.log('ACK received');
client.write(move.backward, function () {
console.log('move backward sent');
client.end();
});
}
});
client.on('end', () => {
console.log('disconnected from server');
});
client.on('error', function (err) {
console.log('Error : ', err);
});
client.on('close', function () {
console.log('socket closed');
});
you can even split code of server and client in two separate files too...
then first start server and then start client
I was using net module to build a simple server/client example. The client side just send a simple message after connection is built, and server side didn't do anything but just print some log, but after that I found the data event in client side got triggered, and the data received is the data it send to the server (but server didn't write anything to client).
Client.js:
var net = require('net');
var port = 3540;
var hostName = "127.0.0.1";
var client = new net.Socket();
client.connect(port, hostName, function() {
console.log("Connected to the remote host: " + hostName + ":" + port);
client.write("hello,world");
client.end();
});
var bytesReceived = 0;
client.on('data', function(data) {
bytesReceived += data.length;
console.log('Received bytes: ' + data.length + ', total bytes received: ' + bytesReceived);
console.log(data.toString())
})
client.on('error', function(error) {
console.log(error);
client.destroy();
});
client.on('close', function() {
console.log('Closed connection');
})
server.js:
var net = require('net');
port = 3540;
var log = function(who, what) {
return function() {
var args = Array.prototype.slice.call(arguments);
console.log('[%s on %s]', who, what, args);
};
};
var count = 0
var echo = function (socket) {
socket.on('end', function() {
console.log('recevied a FIN packet');
socket.end();
});
socket.on('data', function(data) {
console.log(count + ': received bytes: ' + data.length);
count++;
});
socket.on('error', function(error) {
console.log(error);
socket.destroy();
});
socket.on('close', function() {
console.log('connection has been closed!');
});
socket.pipe(socket);
}
var server = net.createServer(echo);
server.listen(port); // port or unix socket, cannot listen on both with one server
server.on('listening', function() {
var ad = server.address();
if (typeof ad === 'string') {
console.log('[server on listening] %s', ad);
} else {
console.log('[server on listening] %s:%s using %s', ad.address, ad.port, ad.family);
}
});
server.on('connection', function(socket) {
server.getConnections(function(err, count) {
console.log('%d open connections!', count);
});
});
server.on('close', function() { console.log('[server on close]'); });
server.on('err', function(err) {
console.log(err);
server.close(function() { console.log("shutting down the server!"); });
});
After that the client print out:
Connected to the remote host: 127.0.0.1:3540
Received bytes: 11, total bytes received: 11
hello,world
Closed connection
but server didn't write anything to client
It does:
socket.pipe(socket)
This will echo the data received from the client (represented by socket) back to the client.
I have two commands to send to server, first move forward, get the acknowledgment and then send next command move backward. I have written two separate java script files do achieve this. Can it is possible to write in single function. I am trying below code but only move forward command is sent to server.
var net = require('net');
var HOST = '127.0.0.1';
var PORT = 1850;
var client = new net.Socket();
client.connect(PORT, HOST, function() {
console.log('CONNECTED TO: ' + HOST + ':' + PORT);
client.write('READER_FWD');
//client.end();
});
client.on('data', function(data) {
console.log('DATA: ' + data);
//client.destroy();
//
if (data == 'ACK')
{
console.log('DATA1: ' + data);
client.end();
console.log('DATA2: ' + data);
client.connect(PORT, HOST, function() {
console.log('CONNECTED TO: ' + HOST + ':' + PORT);
client.write('READER_BWD');
//client.end();
console.log('DATA3: ' + data);
});
}
client.end();
});
client.on('end', function() {
console.log('disconnected from server');
});
client.on('error', function(err) {
console.log(err)
});
I have updated the code, as you rightly pointed out connection is getting close while writing, i have added some delay.
var net = require('net');
var config = {
host: '127.0.0.1',
port: 1850
};
var move = {
forward: 'READER_FWD',
backward: 'READER_BWD'
};
var client = new net.Socket();
client.connect({
host: config.host,
port: config.port
}, function () {
console.log('connected to ' + config.host + ':' + config.port);
client.write(move.forward, function () {
console.log('move forward command sent');
});
});
client.on('data', function (data)
{
var str = data.toString();
if (str === 'ACK')
{
setTimeout(function()
{
console.log('ACK received');
client.write(move.backward, function ()
{
console.log('move backward sent');
client.end();
});
}, 3000);
}
});
client.on('error', function (err) {
console.log('Error : ', err);
});
client.on('close', function () {
console.log('socket closed');
});
You don't have to end your socket and re-open it again in your 'data' listener. You can keep the same socket.
Here is my client.js file which sends the commands:
var net = require('net');
var config = {
host: '127.0.0.1',
port: 1850
};
var move = {
forward: 'READER_FWD',
backward: 'READER_BWD'
};
var client = new net.Socket();
client.connect({
host: config.host,
port: config.port
}, function () {
console.log('connected to ' + config.host + ':' + config.port);
client.write(move.forward, function () {
console.log('move forward command sent');
});
});
client.on('data', function (data) {
var str = data.toString();
if (str === 'ACK') {
console.log('ACK received');
client.write(move.backward, function () {
console.log('move backward sent');
client.end();
});
}
});
client.on('error', function (err) {
console.log('Error : ', err);
});
client.on('close', function () {
console.log('socket closed');
});
The connect() method connects the socket to the server and send the forward command to it. It's exactly the same as yours.
Then, the problem comes from your 'data' listener. Your data listener must do the following things (as you mentionned in your description):
Get data from the server
If it's the ACK message: send the backward command
Then, close the connection (if needed; if not, keep it alive)
Be careful to the following point: the Socket nodejs documentation for the event 'data' says that we are receiving a Buffer. So you need to convert it to a String to compare with another String, using for this the .toString() method of the Buffer.
Thus, as is the Nodejs net.Socket is used with events, I don't think it is possible to send the forward command, listen to the 'data' event and send the backward command.
First, it is not a good idea, because you will put the on 'data' listener after the connection and it is possible that you will miss some data!
Secondly, as it is event based, you should create your architecture that follows the process :)
Below is my code for the server:
var net = require('net');
var port = 1850;
var move = {
forward: 'READER_FWD',
backward: 'READER_BWD'
};
var server = net.createServer(function (client) {
console.log('client connected');
client.on('end', function () {
console.log('client disconnected');
});
client.on('data', function (data) {
var str = data.toString();
if (str === move.forward) {
console.log('move forward command received');
client.write('ACK', function () {
console.log('ACK sent');
});
} else if (str === move.backward) {
console.log('move backward command received: do nothing...');
} else {
console.log('unknown received message: ', str);
}
});
});
server.listen(port, function () { //'listening' listener
console.log('server bound on port: ' + port);
});
Here are also the outputs if needed:
Server:
server bound on port: 1850
client connected
move forward command received
ACK sent
move backward command received: do nothing...
client disconnected
Client:
connected to 127.0.0.1:1850
move forward command sent
ACK received
move backward sent
socket closed
I hope it answers the question. Feel free to ask if there is anything.