node js incoming request sourceIP

Depending on whether the request is made by a proxy forward or direct connection the source ip address may be stored at different places. You have to check req.header['x-forwarded-for'] first and then req.connection.remoteAddress. An example function is shown in this gist.

Here is a working example:

var http = require('http');

var getClientIp = function(req) {
  var ipAddress = null;
  var forwardedIpsStr = req.headers['x-forwarded-for'];
  if (forwardedIpsStr) {
    ipAddress = forwardedIpsStr[0];
  }
  if (!ipAddress) {
    ipAddress = req.connection.remoteAddress;
  }
  return ipAddress;
};

var server = http.createServer();

server.on('request', function(req, res) {
  console.log(getClientIp(req));
  res.writeHead(200, {'Content-Type': 'text/plain'});
  return res.end('Hello World\n');
});

server.listen(9000, 'localhost');

the getClientIp function was taken from here with some minor changes. Note that the contents of x-forwarded-for is an array containing proxy IPs, (read more here), so you may wish to inspect more than the first element.