init

.dockerignore

+*
+!index.js
+!package.json
+!yarn.lockxw
\ No newline at end of file

.gitignore

+node_modules
\ No newline at end of file

Dockerfile

+FROM mhart/alpine-node:10 as base
+WORKDIR /usr/src
+COPY package.json yarn.lock ./
+RUN yarn --production
+
+FROM mhart/alpine-node:base-10
+WORKDIR /usr/src
+COPY --from=base /usr/src .
+COPY . .
+CMD node index.js
+EXPOSE 20000:20000/udp

index.js

+const PORT = 20000;
+const MULTICAST_ADDR = "233.255.255.255";
+
+const dgram = require("dgram");
+const process = require("process");
+
+const socket = dgram.createSocket({ type: "udp4", reuseAddr: true });
+
+socket.bind(PORT);
+
+socket.on("listening", function() {
+  socket.addMembership(MULTICAST_ADDR);
+  socket.setBroadcast(true)
+  setInterval(sendMessage, 2500);
+  const address = socket.address();
+  console.log(
+    `UDP socket listening on ${address.address}:${address.port} pid: ${
+      process.pid
+    }`
+  );
+});
+
+function sendMessage() {
+  const message = Buffer.from(`docker  ${process.pid}`);
+  socket.send(message, 0, message.length, PORT, MULTICAST_ADDR, function() {
+    // console.info(`Sending message "${message}"`);
+  });
+}
+
+socket.on("message", function(message, rinfo) {
+  console.info(`Message from: ${rinfo.address}:${rinfo.port} - ${message}`);
+});
\ No newline at end of file

package.json

+{
+  "name": "membership-client",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index.js",
+    "test": "node test.js"
+  },
+  "author": "Aria <arshiam2828@gmail.com>",
+  "license": "MIT",
+  "dependencies": {
+    "dgram": "^1.0.1"
+  }
+}

yarn.lock

+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+dgram@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/dgram/-/dgram-1.0.1.tgz#37f3b200f8033a5ff759303089c81ce361b651c3"