router.js

var HTTPParser = process.binding('http_parser').HTTPParser;
var net = require('net');
var path = require('path');
var sys = require('sys');
var Worker = require('webworker/webworker').Worker;

var VHOSTS = ['foo.bar.com', 'baz.bizzle.com'];
var WORKERS = {};

VHOSTS.forEach(function(vh) {
    WORKERS[vh] = new Worker(path.join(__dirname, 'worker.js'));
});

net.createServer(function(s) {
    var hp = new HTTPParser('request');
    hp.data = {
        'headers' : {
        },
        'partial' : {
            'field' : '',
            'value' : ''
        }
    };

    var seenData = '';

    hp.onURL = function(buf, start, len) {
        var str = buf.toString('ascii', start, start + len);

        if (hp.data.url) {
            hp.data.url += str;
        } else {
            hp.data.url = str;
        }
    };

    hp.onHeaderField = function(buf, start, len) {
        if (hp.data.partial.value) {
            hp.data.headers[hp.data.partial.field] = hp.data.partial.value;
            hp.data.partial = {
                'field' : '',
                'value' : ''
            };
        }

        hp.data.partial.field += buf.toString(
            'ascii', start, start + len
        ).toLowerCase();
    };

    hp.onHeaderValue = function(buf, start, len) {
        hp.data.partial.value += buf.toString(
            'ascii', start, start + len
        ).toLowerCase();
    };

    hp.onHeadersComplete = function(info) {
        // Clean up partial state
        if (hp.data.partial.field.length > 0 &&
            hp.data.partial.value.length > 0) {
            hp.data.headers[hp.data.partial.field] = hp.data.partial.value;
        }

        delete hp.data.partial;

        hp.data.version = {
            'major' : info.versionMajor,
            'minor' : info.versionMinor
        };

        hp.data.method = info.method;
        hp.data.upgrade = info.upgrade;

        if ('host' in hp.data.headers &&
            hp.data.headers.host in WORKERS) {
            s.pause();

            WORKERS[hp.data.headers.host].postMessage(
                seenData, s.fd
            );
        } else {
            s.write(
                'HTTP/' + info.versionMajor + '.' + info.versionMinor + ' ' +
                '400 Host not found\r\n'
            );
            s.write('\r\n');
            s.end();
        }
    };

    s.ondata = function(buf, start, end) {
        seenData += buf.toString('ascii', start, end);

        var ret = hp.execute(buf, start, end - start);
        
        if (ret instanceof Error) {
            s.destroy(ret);
            return;
        }
    };
}).listen(8080);

worker.js

var Buffer = require('buffer').Buffer;
var http = require('http');
var net = require('net');
var sys = require('sys');

var srv = http.createServer(function(req, resp) {
    resp.writeHead(200, {'Content-Type' : 'text/plain'});
    resp.write('Hello, vhost world!\n');
    resp.end();
});

onmessage = function(msg) {
    var s = new net.Stream(msg.fd);
    s.type = srv.type;
    s.server = srv;
    s.resume();

    srv.emit('connection', s);
    s.emit('data', msg.data);
    s.ondata(new Buffer(msg.data, 'ascii'), 0, msg.data.length);
};

It'd work like this with the node-webworker pull req I just sent you: http://gist.github.com/486260