client.js

var
  PARALLEL_CONNECTS = 10,

  http = require('http'),
  sys = require('sys'),
  connectionCount = 0,
  messageCount = 0;
  lastMessages = 0;

function addClient() {
  var client = http.createClient(8000);
  client.setTimeout(0);
  client.addListener('connect', function() {
    connectionCount++;
    addClient();
  });

  client.addListener('close', function() {
    connectionCount--;
  });

  var request = client.request("GET", "/", {"host": "localhost"});
  request.finish(function (res) {
    res.addListener('body', function() {
      messageCount++;
      lastMessages++;
    });
  });
};

for (var i = 0; i < PARALLEL_CONNECTS; i++) {
  addClient();
}

var lastCheck = +(new Date);
setInterval(function() {
  var
    duration = ((+(new Date) - lastCheck) / 1000),
    messagesPerSec = (lastMessages / duration).toFixed(0);

  sys.puts(
    (new Date).toISOString()+": "+
    connectionCount+' connections, '+
    messageCount+' messages received ('+
    messagesPerSec+' messages / sec)'
  );

  lastMessages = 0;
  lastCheck = +(new Date);
}, 1000);

monitor.sh

# http://www.metabrew.com/article/a-million-user-comet-application-with-mochiweb-part-2/

SERVERPID=`pgrep -f 'node server.js'`; while [ 1 ] ; do NUMCON=`netstat -n | awk '/ESTABLISHED/ && $4=="127.0.0.1:8000"' | wc -l`; MEM=`ps -o rss= -p $SERVERPID`; echo -e "`date`\t`date +%s`\t$MEM\t $NUMCON"; sleep 1; done

server.js

var http = require('http');

var server = http.createServer(function(req, res) {
  req.connection.setTimeout(0);
  res.sendHeader(200, {'Content-Type': 'text/plain'});
  setInterval(function() {
    res.sendBody("Hello\n");
    res.flush();
  }, 10000);
});
server.listen(8000);

sysctl.conf

# See http://www.metabrew.com/article/a-million-user-comet-application-with-mochiweb-part-3/

net.core.rmem_max = 33554432
net.core.wmem_max = 33554432
net.ipv4.tcp_rmem = 4096 16384 33554432
net.ipv4.tcp_wmem = 4096 16384 33554432
net.ipv4.tcp_mem = 786432 1048576 26777216
net.ipv4.tcp_max_tw_buckets = 360000
net.core.netdev_max_backlog = 2500
vm.min_free_kbytes = 65536
vm.swappiness = 0
net.ipv4.ip_local_port_range = 1024 65535