Develop Reference

How to send udp packages using nodejs?

Well, I have a small route that should send an UDP package and print a confirmation. According to the documentation on the node, the following should work fine:
const dgram = require('dgram');
export async function sendUDP(sess, parameters: {}, res) {
const client = dgram.createSocket('udp4');
client.send('Hello World!',0, 12, 12000, '127.0.0.1', function(err, bytes) {
client.close();
});
//res is the response object from express
return res.send("Send udp packet");
}
It should send an UDP request to port 12000 on the callback IP (local machine). And also send a reply that the UDP packet has been sent.
I notice the reply Send udp packet received at postman when I post to the correct URL. So that is working.
However, the UDP packages seem to be lost, using tcpdump on my local ubuntu results in nothingness:
sudo tcpdump -n udp port 12000
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on wlp5s0, link-type EN10MB (Ethernet), capture size 262144 bytes
0 packets captured
0 packets received by filter
0 packets dropped by kernel
(While tcpdump has been kept running during the test of the functions of course). Where do the UDP requests go? What happened?
I wish to have a life logger so that I can test nodejs applications using udp easily.

You need to tell tcpdump the interface it needs to listen.
tcpdump -i lo udp port 12000
lo is the interface for localhost.
More information in this link
You can use wireshark if you want to save the traffic log.
I use '!(udp.port == 53 || tcp.port == 53) && udp' as a filter to look only to udp packet.
I add this code to my server and send the udp packet there to print the content
const dgram = require('dgram');
const serverUDP = dgram.createSocket('udp4');
serverUDP.on('error', (err) => {
console.log(`serverUDP error:\n${err.stack}`);
serverUDP.close();
});
serverUDP.on('message', (msg, rinfo) => {
console.log(`serverUDP got: ${msg} from ${rinfo.address}:${rinfo.port}`);
});
serverUDP.on('listening', () => {
const address = serverUDP.address();
console.log(`serverUDP listening ${address.address}:${address.port}`);
});
serverUDP.bind(3001);
It is the code sample from the node documentation

NodeJs Server flooded with UDP Broadcasts, doesn't send response

I am building a system using an ESP8266/NodeMcu module (similar to an Arduino, just with networking capabilities) and a NodeJs server running on the local network.
To discover the IP address of the server, I'm trying to use UDP broadcasting on the NodeMcu module. The idea is to send out a message on the local broadcasting IP (e.g. 192.168.1.255). The server then receives the message and sends a response, confirming that it is the server. This way, the NodeMcu knows the direct address of the server for further communication.
The problem is, that the server is completely flooding itself with the same message whenever it receives the first message from the NodeMcu, while the NodeMcu actually sends out a message only once a second.
It looks like this on the NodeMcu side:
[UDP] Sending UDP Broadcast on IP: 192.168.43.255, Port: 8080, Message: ESP8266 UDP Server Discovery Broadcast
The server outputs something like this, many times a second:
[10:33:07] 127.0.0.1:8080 # service discovery : ESP8266 UDP Server Discovery Broadcast
[10:33:07] 127.0.0.1:8080 # service discovery : ESP8266 UDP Server Discovery Broadcast
[10:33:07] 127.0.0.1:8080 # service discovery : ESP8266 UDP Server Discovery Broadcast
It doesn't make sense that it's receiving that many messages, especially because it's apparently coming from 127.0.0.1 and not the IP of the NodeMcu. It also doesn't send out any response.
I tried to receive the broadcast on my phone with a UDP Monitor app, an application called Packet Sender and the Linux Terminal. It all worked fine, and sending a manual response triggered the acknowledgement on the NodeMcu.
So I'm thinking there has to be some kind of error with the server, or with the network I'm using. The server is running on Linux on my computer, while I'm hosting the network via a hotspot on my phone (my real WiFi network blocked UDP broadcasting). The Linux firewall is turned off.
I'm no expert in JavaScript or NodeJs by any means and the server was written by someone I'm working with, but he has no clue either. Anyway, this is the important part on the server:
client.on('listening', function () {
var address = client.address();
debugMessage(
format('Service discovery running on port %s', config.port)
);
client.setBroadcast(true);
});
client.on('message', function (message, rinfo) {
debugMessage(
format('%s:%s # service discovery : %s', rinfo.address, rinfo.port, message)
);
client.send(message, 0, message.length, rinfo.port, rinfo.ip);
});
client.bind(config.port);
The code on the NodeMcu looks like this:
#include <ESP8266WiFi.h> // WiFi library
#include <WiFiUdp.h> // UPD functionality
// UDP variables
WiFiUDP udp;
unsigned int localUdpPort = 8080;
char incomingPacket[255];
const char broadcastMessage[] = "ESP8266 UDP Server Discovery Broadcast";
// Server details - written to when the server is found
IPAddress serverIp = ~WiFi.subnetMask() | WiFi.gatewayIP(); // Use Broadcast Address as default in case the UDP service discovery isn't working as intended
unsigned int serverPort = localUdpPort; // Use local port as default in case the UDP service discovery ins't working as intended
void setupWiFi()
{
WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
#if LOGGING
Serial.println("Connecting to network: " + (String) WIFI_SSID);
#endif
while (WiFi.status() != WL_CONNECTED)
{
delay(100);
}
#if LOGGING
Serial.print("Connected to network, Local IP Address: ");
Serial.println(WiFi.localIP());
#endif
udp.begin(localUdpPort); // begin listening on UDP port
#if LOGGING
Serial.printf("Now listening at IP %s, UDP port %d\n", WiFi.localIP().toString().c_str(), localUdpPort);
#endif LOGGING
}
// Discover the server via a UDP broadcast, and store it's IP and Port in the local network in field variables for later use
// IMPORTANT - For the server to work, the Linux Firewall has to be disabled!!!
void discoverServer()
{
changeColor(PURPLE, false); // change the color of the RGB status LED to signal that the program is searching for the server
bool serverFound = false; // stop when the server is found
IPAddress broadcastIp = ~WiFi.subnetMask() | WiFi.gatewayIP(); // Get the Broadcast IP of the local network (e.g. 192.168.0.255)
while (!serverFound)
{
// Send UDP Broadcast
udp.beginPacket(broadcastIp, localUdpPort);
udp.write(broadcastMessage);
udp.endPacket();
#if LOGGING
Serial.printf("[UDP] Sending UDP Broadcast on IP: %s, Port: %d, Message: %s\n", broadcastIp.toString().c_str(), localUdpPort, broadcastMessage);
#endif
delay(1000); // Pause a few milliseconds to avoid flooding the network
// Receive UDP packets
int packetSize = udp.parsePacket();
if (packetSize > 0)
{
// Read incoming UDP Packet
int len = udp.read(incomingPacket, 255);
if (len > 0)
{
incomingPacket[len] = 0;
}
#if LOGGING
Serial.printf("[UDP] Received %d bytes from %s, port %d\n", packetSize, udp.remoteIP().toString().c_str(), udp.remotePort());
Serial.printf("[UDP] Packet contents: %s\n", incomingPacket);
#endif
// Check if the received message is from the server we are searching for
if (strcmp(incomingPacket, broadcastMessage) == 0)
{
serverIp = udp.remoteIP();
serverPort = udp.remotePort();
#if LOGGING
Serial.printf("[UDP] Found Server on IP: %s, Port: %d\n", serverIp.toString().c_str(), serverPort);
#endif
serverFound = true;
changeColor(YELLOW, false); // Change status color of RGB LED back to yellow
}
}
}
}
I'm really wondering if there is something wrong with the server, the network or the NodeMcu. Especially because every other method I tried worked perfectly, just not when I'm sending it from the NodeMcu. Any help is very much appreciated!

It turned out that there was an error in the server code.
Instead of
client.send(message, 0, message.length, rinfo.port, rinfo.ip);
it should have been
client.send(message, 0, message.length, rinfo.port, rinfo.address);
The server didn't know rinfo.ip, so it spammed itself with the same message over and over again.

Handshake error with WebSocket python server and JS client

I am trying to setup a communication between a python script (that will do a lot of computation on data that cannot be done in javascript and send send that data as a json) and a javascript client.
I have the following code for my python server:
import socket
import sys
from thread import *
HOST = '' # Symbolic name meaning all available interfaces
PORT = 9888 # Arbitrary non-privileged port
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Socket created'
#Bind socket to local host and port
try:
s.bind((HOST, PORT))
except socket.error as msg:
print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]
sys.exit()
print 'Socket bind complete'
#Start listening on socket
s.listen(10)
print 'Socket now listening'
#Function for handling connections. This will be used to create threads
def clientthread(conn):
#Sending message to connected client
conn.send('Welcome to the server. Type something and hit enter\n') #send only takes string
#infinite loop so that function do not terminate and thread do not end.
while True:
#Receiving from client
data = conn.recv(1024)
reply = 'OK...' + data
if not data:
break
conn.sendall(reply)
#came out of loop
conn.close()
#now keep talking with the client
while 1:
#wait to accept a connection - blocking call
conn, addr = s.accept()
print 'Connected with ' + addr[0] + ':' + str(addr[1])
#start new thread takes 1st argument as a function name to be run, second is the tuple of arguments to the function.
start_new_thread(clientthread ,(conn,))
s.close()
And the following code for my javascript client:
var connection = new WebSocket('ws://127.0.0.1:8999');
connection.onopen = function () {
connection.send('Hello'); // Send the message to the server
};
I get the following error from my javascript client:
Error during WebSocket handshake: net::ERR_INVALID_HTTP_RESPONSE
And the following output from my python server
Socket created
Socket bind complete
Socket now listening
Connected with 127.0.0.1:53956
Unhandled exception in thread started by <function clientthread at 0x10abac578>
Traceback (most recent call last):
File "server.py", line 71, in clientthread
data = conn.recv(1024)
socket.error: [Errno 54] Connection reset by peer
Would anyone know what is wrong?
Edit: forgot to mention that I have seen this SO Post before, but my problem is not the same, or rather should I say that the error encountered by OP is not the same as mine.

A WebSocket is a not the same as a plain TCP socket you create. WebSocket is a protocol on top of TCP instead which starts with a HTTP handshake and then continues with a framing based protocol. If you want to implement a WebSocket server in Python you need to implement this protocol as specified in RFC 6455 or use existing WebSocket libraries.
An example server-side python code using WebSocket is:
import asyncio
import websockets
async def handle_message(message):
print(message)
async def consumer_handler(websocket, path):
while True:
message = await websocket.recv()
await handle_message(message)
start_server = websockets.serve(consumer_handler, 'localhost', 8765)
asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_forever()

Unable to connect to Mosquitto over Websocket

I am unable to connect to my local Mosquitto 1.4.10 broker from a JavaScript client over a Websocket.
The same JavaScript client is successfully connecting to the public broker at test.mosquitto.org on port 8080 over a Websocket.
The MQTT protocol connection on port 1883 is working fine, which I tested using mosquitto_pub and mosquitto_sub.
My broker is set up within a VirtualBox running Ubuntu 14.04.
I have libwebsockets installed on the same virtual machine.
My local broker was compiled with WITH_WEBSOCKETS:=yes in the config.mk file
I am loading the JavaScript client web page from the same virtual machine from a Firefox browser and seeing the following error message in the browser console:
Firefox can't establish a connection to the server at
ws://localhost:8080/mqtt
Your suggestions on fixing this will be greatly appreciated.
Thanks.
Here is my Mosquitto .conf file:
port 1883
listener 8080
protocol websockets
log_type all
websockets_log_level 1023
connection_messages true
Here is the Mosquitto server's log (with websockets logging level set to 1023, and verbose logging turned on - no messages appear when I load the JavaScript web page):
1481381105: mosquitto version 1.4.10 (build date 2016-12-10
18:47:37+0530) starting
1481381105: Config loaded from /etc/mosquitto/mosquitto.conf.
1481381105: Opening websockets listen socket on port 8080.
1481381105: Initial logging level 1023
1481381105: Libwebsockets version: 2.1.0 manavkumarm#manav-alljoyn
1481381105: IPV6 not compiled in
1481381105: libev support not compiled in
1481381105: libuv support not compiled in
1481381105: Threads: 1 each 1024 fds
1481381105: mem: platform fd map: 4096 bytes
1481381105: Compiled with OpenSSL support
1481381105: Creating Vhost 'default' port 8080, 3 protocols, IPv6 off
1481381105: Using non-SSL mode
1481381105: Listening on port 8080
1481381105: mem: per-conn: 376 bytes + protocol rx buf
1481381105: canonical_hostname = mqtt
1481381105: Opening ipv4 listen socket on port 1883.
1481381105: Opening ipv6 listen socket on port 1883.
Here is the JavaScript source code:
<html>
<body>
<script src="mqttws31.js"></script>
<script>
try
{
// Create a client instance
console.log("Creating client object...");
client = new Paho.MQTT.Client("localhost", Number(8080), "manav");
//client = new Paho.MQTT.Client("test.mosquitto.org", Number(8080), "manav");
// set callback handlers
console.log("Setting handlers...");
client.onConnectionLost = onConnectionLost;
client.onMessageArrived = onMessageArrived;
// connect the client
console.log("Connecting...");
client.connect( {
onSuccess: onConnect,
mqttVersion: 4
});
}
catch (e)
{
console.log("Error: " + e.description);
}
// called when the client connects
function onConnect()
{
// Once a connection has been made, make a subscription and send a message.
console.log("Connected");
setTimeout( function() {
client.subscribe("world");
message = new Paho.MQTT.Message("Hello");
message.destinationName = "world";
client.send(message);
//client.disconnect();
}, 5000);
}
// called when the client loses its connection
function onConnectionLost(responseObject) {
if (responseObject.errorCode !== 0) {
console.log("Connection lost: " + responseObject.errorMessage);
}
}
// called when a message arrives
function onMessageArrived(message) {
console.log("Received Message: " + message.payloadString);
client.disconnect();
}
</script>
<h1>My MQTT Websockets Example</h1>
</body>
</html>

I see I am little bit late on answer.
MQTT's port for websocket is 1884 or something else, you have 8080. Maybe thats the problem.
Isnt 8080 a reserved TCP port?
Also, I know you have javascript code, but its paho. I was able to make publisher(it uses same class like subscriber so it must be on subscriber side too - this is just assumption though) work on websockets with paho python client which must be initialized with defining transport parameter. -> communicating with browser(see below for javascript)
mqtt.Client(transport='websockets')
Leaving that parameter MQTT assumes using TCP
mqtt.Client()
Also:
Config on my broker:
# Place your local configuration in /etc/mosquitto/conf.d/
#
# A full description of the configuration file is at
# /usr/share/doc/mosquitto/examples/mosquitto.conf.example
pid_file /var/run/mosquitto.pid
persistence true
persistence_location /var/lib/mosquitto/
log_dest file /var/log/mosquitto/mosquitto.log
include_dir /etc/mosquitto/conf.d
listener 1883
listener 1884
protocol websockets
I found my very old Javascript with paho-mqtt. It was working, so I just put it here.
Its subscriber and publisher at the same time. Together with the config, It was working like charm.
class sub{
constructor(hostname,port,clientid,topic){
this.buffer = []
this.hostname=hostname;
this.port=port;
this.clientid = clientid;
this.topic = topic;
this.client = new Paho.MQTT.Client(hostname,port, clientid);
// set callback handlers
this.client.onConnectionLost = this.onConnectionLost;
this.client.onMessageArrived = this.onMessageArrived.bind(this);
// connect the client
this.client.connect({onSuccess:this.onConnect});
}
onConnect(){
console.log('OnConnect');
}
onConnectionLost(responseObject) {
if (responseObject.errorCode !== 0) {
console.log("onConnectionLost:"+responseObject.errorMessage);
}
}
onMessageArrived(message) {
console.log("onMessageArrived:"+message.payloadString);
this.buffer.push(JSON.parse(message.payloadString));
}
subsribe(){
this.client.subscribe(this.topic)
}
publish(message){
console.log(message)
var mg = new Paho.MQTT.Message(JSON.stringify(message));
mg.destinationName = this.topic;
this.client.send(mg);
}
}
var x
x = new sub('xx.xx.xx.xx',1884,'clientID','LED');
function on(){
x.publish({'LED':'ON'});
}
function off(){
x.publish({'LED':'OFF'});
}

Indesign javascript Socket always performs requests using host: localhost

I'm trying to use a Socket connection to read a file on a remote website. So far, my code:
conn = new Socket;
if( conn.open( 'example.com:80' ) ) {
conn.write( 'GET /indesign-page/ HTTP/1.0' + "\n\n" );
reply = conn.read(999999);
conn.close();
} else {
alert( 'Problem connecting to server' );
}
The socket connects to example.com fine, but the request comes across as this:
GET http://localhost/indesign-page/ HTTP/1.0
when it should be this:
GET http://example.com/indesign-page/ HTTP/1.0
I've tried changing the conn.write parameters to 'GET http://example.com/indesign-page/ ...', but then it comes across as:
GET http://localhosthttp://example.com/indesign-page/ HTTP/1.0
The webserver requires that the host be set correctly to serve correctly.

You need to set the "Host" header.
conn.write( 'GET /indesign-page/ HTTP/1.0' + "Host: example.com\r\n" + "\n\n" );
Because conn.open( 'example.com:80' ) means find example.com's server ip then connect that ip address at 80 port, so the web server does not know that you had resolved example.com before connected to it.

Do you need to use a manual socket object? On Adobe's Community Site there's a mention to this already created FTP Script where you could call a GET or PUT to a file on a FTP server.
Otherwise which OS are you using? If you'll always be on a Mac, you could shell out to an AppleScript command and place the file anywhere you'd like:
var command = 'do shell script "curl http://localhost/indesign-page"';
var response = app.doScript(command, ScriptLanguage.APPLESCRIPT_LANGUAGE);
The nice thing about the AppleScript is that you can execute the command manually using the AppleScript Editor (or Script Editor if you're earlier than 10.6).