This code sets up a project environment by determining the user's home directory path, appending a project directory path, initializing a server, and establishing a connection to the server using Socket.IO. It then sends a "close" event to the server, likely to terminate the connection.

Cell 4

var PROFILE_PATH = process.env.HOME || process.env.HOMEPATH || process.env.USERPROFILE;
var project = PROFILE_PATH + '/universal';
var server = require(project + '/src/server/sockify-server.js').sockifyServer(8000);
var client = require('socket.io-client').connect('https://localhost:8000');
client.emit('close');

typescript
// Import required modules
import * as path from 'path';
import * as fs from 'fs';
import * as process from 'process';
import { createServer } from 'http';
import { Server } from'socket.io';
import { connect } from'socket.io-client';

// Define environment variables
const HOME = process.env.HOME || process.env.HOMEPATH || process.env.USERPROFILE;

// Define project path
const PROJECT_PATH = path.join(HOME, 'universal');

// Define server and client variables
let server: Server;
let client: any;

// Define server port
const PORT = 8000;

/**
 * Start the server.
 */
async function startServer() {
  // Check if project path exists
  if (!fs.existsSync(PROJECT_PATH)) {
    console.error('Project path does not exist');
    process.exit(1);
  }

  // Import server module
  const serverModule = require(path.join(PROJECT_PATH,'src','server','sockify-server.js'));
  server = serverModule.sockifyServer(PORT);

  // Listen for close event
  server.on('connection', (socket) => {
    socket.on('close', () => {
      console.log('Server closed');
    });
  });

  // Start the server
  await new Promise((resolve) => server.listen(PORT, () => resolve()));
}

/**
 * Connect to the server.
 */
async function connectToServer() {
  try {
    client = connect('https://localhost:' + PORT);
    client.emit('close');
  } catch (error) {
    console.error('Error connecting to server:', error);
  }
}

// Start the server and connect to it
async function main() {
  try {
    await startServer();
    await connectToServer();
  } catch (error) {
    console.error('Error starting server or connecting to it:', error);
  }
}

main();

Code Breakdown

Environment Variable

var PROFILE_PATH = process.env.HOME || process.env.HOMEPATH || process.env.USERPROFILE;

• This line sets a variable PROFILE_PATH to the user's home directory path.
• It checks the following environment variables in order:
  • HOME
  • HOMEPATH
  • USERPROFILE
  • Assigns the first non-null value to PROFILE_PATH

Project Path Construction

var project = PROFILE_PATH + '/universal';

• This line appends the string /universal to the PROFILE_PATH variable to form the project directory path.

Server Initialization

var server = require(project + '/src/server/sockify-server.js').sockifyServer(8000);

• This line imports the sockify-server.js module from the project's src/server directory.
• It then calls the sockifyServer function with the port number 8000 and assigns the returned server object to the server variable.

Client Initialization

var client = require('socket.io-client').connect('https://localhost:8000');

• This line imports the socket.io-client module and uses it to establish a connection to a Socket.IO server on https://localhost:8000.

Emitted Event

client.emit('close');

• This line sends a close event to the connected Socket.IO server.