Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Node.js TCP client and server example
/*
In the node.js intro tutorial (http://nodejs.org/), they show a basic tcp
server, but for some reason omit a client connecting to it. I added an
example at the bottom.
Save the following server in example.js:
*/
var net = require('net');
var server = net.createServer(function(socket) {
socket.write('Echo server\r\n');
socket.pipe(socket);
});
server.listen(1337, '127.0.0.1');
/*
And connect with a tcp client from the command line using netcat, the *nix
utility for reading and writing across tcp/udp network connections. I've only
used it for debugging myself.
$ netcat 127.0.0.1 1337
You should see:
> Echo server
*/
/* Or use this example tcp client written in node.js. (Originated with
example code from
http://www.hacksparrow.com/tcp-socket-programming-in-node-js.html.) */
var net = require('net');
var client = new net.Socket();
client.connect(1337, '127.0.0.1', function() {
console.log('Connected');
client.write('Hello, server! Love, Client.');
});
client.on('data', function(data) {
console.log('Received: ' + data);
client.destroy(); // kill client after server's response
});
client.on('close', function() {
console.log('Connection closed');
});
@amoopoori
Copy link

amoopoori commented Sep 13, 2018

i need to listen on 5 5 different ports

@stochastic-thread
Copy link

stochastic-thread commented Oct 9, 2018

you could probably set up some kind of nginx proxy_pass redirection scheme that forwards all incoming http requests that come in on a given set of specific ports to a single port that your web server socket has bound to

I've done this for a single port to port redirection (in my use case it was coupled with https termination but that is irrelevent to your situation.)

in principle I don't see why that wouldn't work. or just run 5 web servers but thats misguided if they are just doing the same work, depending on what your scaling needs are.

@klys
Copy link

klys commented Nov 10, 2018

client.write do not really send data to the server, it just writes over the same socket of the client.

---edit----

Ok, I just figured it out the server is an ECHO server, which means, it sends what it received.

so client.write send information to the server and the server response it, the problem I was having is: the event server.on('data') was not being triggered, that is because server.on('data') do not hold the SOCKET of the server, it held in the moment of the initialization of the server in net.CreateServer callback function.

That is it.

@adrwh
Copy link

adrwh commented Feb 17, 2019

Hello, i want to use this to create a 3 way chat service on the command line. I created the server using your code, and connected to it from two terminal windows using the ncat, however the server only echo's each clients request back to that particular client. I want to echo back to each client, so that it feels like a group chat?

screen shot 2019-02-18 at 7 02 21 am

@whhb
Copy link

whhb commented Feb 18, 2019

This is really fun, I have been playing with this today and you have definitely distracted me. Ignore my previous issue, I have progressed and now have a basic “chat room” with multiple clients.. I have been using ncat as the client, but I need more logic so I’m trying to implement your node client. So far it works, connects to the server and writes the initial text..

But all subsequent message don’t seem to go back to the server?

Apart from the very first client.write how do I send a mother client.write after the user hits enter?

@adrwh
Copy link

adrwh commented Feb 18, 2019

This is really fun, I have been playing with this today and you have definitely distracted me. Ignore my previous issue, I have progressed and now have a basic “chat room” with multiple clients.. I have been using ncat as the client, but I need more logic so I’m trying to implement your node client. So far it works, connects to the server and writes the initial text..

But all subsequent message don’t seem to go back to the server?

Apart from the very first client.write how do I send a mother client.write after the user hits enter?

@rajnisheu
Copy link

rajnisheu commented Sep 14, 2019

newbies who visit this many years later may find this video on youtube helpful to get started with the server side https://www.youtube.com/watch?v=HyGtI17qAjM

@YodaEmbedding
Copy link

YodaEmbedding commented Nov 29, 2019

Is Hello, server! Love, Client. guaranteed to print? It seems like there's a race condition.

Actually, is anything other than E guaranteed to print?

@masvarn
Copy link

masvarn commented Feb 19, 2020

Hi, is it possible to use this to connect to a network share (smb1)?

Copy link

ghost commented Sep 29, 2020

The output:

Connected
Received: Echo server
Hello, server! Love, Client.
Connection closed

all is fine

@hamid814
Copy link

hamid814 commented Jan 15, 2021

this gist was really helpful for me, thank you dude

@henrydcs
Copy link

henrydcs commented Feb 10, 2021

Hi guys and gals,
I'm trying to create a simulator using Javascript for the front end which I can do, but I'm having a hard time with Node.js for the backend. When I click on, say, a Cisco router icon, I want the a physical connection to occur between my PC and the physcial router that is connected via ethernet. It is a laboratory router (no internet connection). I was thinking that I should download the NPM package telnet-client and require it in the node.js file. I don't know what to do from there. I assume I have to require net as well. Will someone help me. Please... Pretty please :)

@terthesz
Copy link

terthesz commented Apr 5, 2021

Please use arrow functions!

@NickTsl
Copy link

NickTsl commented Jul 15, 2021

hello, how can you prevent DDOS attacks on this code?

@ABHINAVABHISHEK
Copy link

ABHINAVABHISHEK commented Sep 6, 2021

how to set tcp headers on request and receive in the server

@zakcodez
Copy link

zakcodez commented Sep 19, 2021

how to set tcp headers on request and receive in the server

I don't think you can set headers with TCP. HTTP maybe what you are looking for

@Raghupathy-max
Copy link

Raghupathy-max commented Apr 19, 2022

'Received: ' + data

I also have a same issue.......

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment