node/test/simple/test-net-keepalive.js

var common = require('../common');
var assert = require('assert');
var net = require('net');

var serverConnection;
var echoServer = net.createServer(function(connection) {
  serverConnection = connection;
  connection.setTimeout(0);
  assert.notEqual(connection.setKeepAlive, undefined);
  // send a keepalive packet after 1000 ms
  connection.setKeepAlive(true, 1000);
  connection.addListener('end', function() {
    connection.end();
  });
});
echoServer.listen(common.PORT);

echoServer.addListener('listening', function() {
  var clientConnection = net.createConnection(common.PORT);
  clientConnection.setTimeout(0);

  setTimeout(function() {
    // make sure both connections are still open
    assert.equal(serverConnection.readyState, 'open');
    assert.equal(clientConnection.readyState, 'open');
    serverConnection.end();
    clientConnection.end();
    echoServer.close();
  }, 1200);
});