text: // Copyright Joyent, Inc. and other Node contributors.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a
  // copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to permit
  // persons to whom the Software is furnished to do so, subject to the
  // following conditions:
  //
  // The above copyright notice and this permission notice shall be included
  // in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  // USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  'use strict';
  const common = require('../common');
  const assert = require('assert');
  const cluster = require('cluster');
  const net = require('net');
  
  if (cluster.isWorker) {
    net.createServer((socket) => {
      socket.end('echo');
    }).listen(0, '127.0.0.1');
  
    net.createServer((socket) => {
      socket.end('echo');
    }).listen(0, '127.0.0.1');
  } else if (cluster.isMaster) {
    const servers = 2;
    const serverPorts = new Set();
  
    // test a single TCP server
    const testConnection = (port, cb) => {
      const socket = net.connect(port, '127.0.0.1', () => {
        // buffer result
        let result = '';
        socket.on('data', (chunk) => { result += chunk; });
  
        // check result
        socket.on('end', common.mustCall(() => {
          cb(result === 'echo');
          serverPorts.delete(port);
        }));
      });
    };
  
    // test both servers created in the cluster
    const testCluster = (cb) => {
      let done = 0;
      const portsArray = Array.from(serverPorts);
  
      for (let i = 0; i < servers; i++) {
        testConnection(portsArray[i], (success) => {
          assert.ok(success);
          done += 1;
          if (done === servers) {
            cb();
          }
        });
      }
    };
  
    // start two workers and execute callback when both is listening
    const startCluster = (cb) => {
      const workers = 8;
      let online = 0;
  
      for (let i = 0, l = workers; i < l; i++) {
        cluster.fork().on('listening', common.mustCall((address) => {
          serverPorts.add(address.port);
  
          online += 1;
          if (online === workers * servers) {
            cb();
          }
        }, servers));
      }
    };
  
    const test = (again) => {
      //1. start cluster
      startCluster(common.mustCall(() => {
        //2. test cluster
        testCluster(common.mustCall(() => {
          //3. disconnect cluster
          cluster.disconnect(common.mustCall(() => {
            // run test again to confirm cleanup
            if (again) {
              test();
            }
          }));
        }));
      }));
    };
  
    test(true);
  }
  