test: fix flaky test-dgram-pingpong

There is no guarantee UDP messages will be received. Accommodate the occasional dropped message. This is a functionality test, not a performance benchmark. Speed up the test by sending 5 messages per server rather than 500. Fixes: #4526

Author: Trott

test/sequential/sequential.status

@@ -10,7 +10,6 @@ prefix sequential
 
 [$system==linux]
 test-vm-syntax-error-stderr : PASS,FLAKY
-test-dgram-pingpong : PASS,FLAKY
 test-http-regr-gh-2928 : PASS,FLAKY
 
 [$system==macos]

test/sequential/test-dgram-pingpong.js

@@ -1,78 +1,62 @@
 'use strict';
-var common = require('../common');
-var assert = require('assert');
-var Buffer = require('buffer').Buffer;
-var dgram = require('dgram');
-
-var debug = false;
-var tests_run = 0;
+const common = require('../common');
+const assert = require('assert');
+const dgram = require('dgram');
 
 function pingPongTest(port, host) {
- var callbacks = 0;
- var N = 500;
- var count = 0;
+ let pingsReceived = 0;
+ let pongsReceived = 0;
+ let done = false;
 
- var server = dgram.createSocket('udp4', function(msg, rinfo) {
- if (debug) console.log('server got: ' + msg +
- ' from ' + rinfo.address + ':' + rinfo.port);
+ const N = 5;
 
- if (/PING/.exec(msg)) {
- var buf = new Buffer(4);
- buf.write('PONG');
- server.send(buf, 0, buf.length,
- rinfo.port, rinfo.address,
- function(err, sent) {
- callbacks++;
- });
- }
+ const server = dgram.createSocket('udp4', function(msg, rinfo) {
+ assert.strictEqual('PING', msg.toString('ascii'));
+ pingsReceived++;
+ server.send('PONG', 0, 4, rinfo.port, rinfo.address);
  });
 
  server.on('error', function(e) {
  throw e;
  });
 
  server.on('listening', function() {
- console.log('server listening on ' + port + ' ' + host);
+ console.log('server listening on ' + port);
 
- const buf = new Buffer('PING');
  const client = dgram.createSocket('udp4');
 
- client.on('message', function(msg, rinfo) {
- if (debug) console.log('client got: ' + msg +
- ' from ' + rinfo.address + ':' + rinfo.port);
- assert.equal('PONG', msg.toString('ascii'));
-
- count += 1;
+ client.on('message', function(msg) {
+ assert.strictEqual('PONG', msg.toString('ascii'));
 
- if (count < N) {
- client.send(buf, 0, buf.length, port, 'localhost');
- } else {
- client.send(buf, 0, buf.length, port, 'localhost', function() {
- client.close();
- });
+ pongsReceived++;
+ if (pongsReceived === N) {
+ done = true;
+ client.close();
  }
  });
 
- client.on('close', function() {
+ client.on('close', common.mustCall(function() {
  console.log('client has closed, closing server');
- assert.equal(N, count);
- tests_run += 1;
+ assert(pingsReceived >= N);
+ assert.strictEqual(pongsReceived, N);
  server.close();
- assert.equal(N - 1, callbacks);
- });
+ }));
 
  client.on('error', function(e) {
  throw e;
  });
 
- console.log('Client sending to ' + port + ', localhost ' + buf);
- client.send(buf, 0, buf.length, port, 'localhost', function(err, bytes) {
- if (err) {
- throw err;
- }
- console.log('Client sent ' + bytes + ' bytes');
- });
- count += 1;
+ console.log('Client sending to ' + port);
+
+ function clientSend() {
+ client.send('PING', 0, 4, port, 'localhost');
+ setImmediate(() => {
+ if (!done)
+ clientSend();
+ });
+ }
+
+ clientSend();
  });
  server.bind(port, host);
 }
@@ -81,9 +65,3 @@ function pingPongTest(port, host) {
 pingPongTest(common.PORT + 0, 'localhost');
 pingPongTest(common.PORT + 1, 'localhost');
 pingPongTest(common.PORT + 2);
-//pingPongTest('/tmp/pingpong.sock');
-
-process.on('exit', function() {
- assert.equal(3, tests_run);
- console.log('done');
-});