Listen on a TCP port or a UNIX socket file in node.js. Handle EADDRINUSE for the socket file by deleting it and re-listening.

listenOnPortOrSocketFile.js

var fs = require('fs')
  , net = require('net')
  , http = require('http')
  , port = process.env.PORT;

var app = function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
};

var server = http.createServer(app).listen(port, function() {
  require('util').log("Listening on " + port);
  
  // downgrade process user to owner of this file
  return fs.stat(__filename, function(err, stats) {
    if (err) throw err;
    return process.setuid(stats.uid);
  });
});

// port is a UNIX socket file
if (isNaN(parseInt(port))) {
  server.on('listening', function() {
    // set permissions
    return fs.chmod(port, 0777);
  });
  
  // double-check EADDRINUSE
  server.on('error', function(e) {
    if (e.code !== 'EADDRINUSE') throw e;
    net.connect({ path: port }, function() {
      // really in use: re-throw
      throw e;
    }).on('error', function(e) {
      if (e.code !== 'ECONNREFUSED') throw e;
      // not in use: delete it and re-listen
      fs.unlinkSync(port);
      server.listen(port);
    });
  });
}