node/test/parallel/test-dgram-close.js

// Copyright Joyent, Inc. and other Node contributors.
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'use strict';
// Ensure that if a dgram socket is closed before the DNS lookup completes, it
// won't crash.

const common = require('../common');
const assert = require('assert');
const dgram = require('dgram');

const buf = Buffer.alloc(1024, 42);

let socket = dgram.createSocket('udp4');
const handle = socket._handle;

// get a random port for send
const portGetter = dgram.createSocket('udp4')
  .bind(0, 'localhost', common.mustCall(() => {
    socket.send(buf, 0, buf.length,
                portGetter.address().port,
                portGetter.address().address);

    assert.strictEqual(socket.close(common.mustCall()), socket);
    socket.on('close', common.mustCall());
    socket = null;

    // Verify that accessing handle after closure doesn't throw
    setImmediate(function() {
      setImmediate(function() {
        console.log('Handle fd is: ', handle.fd);
      });
    });

    portGetter.close();
  }));