Example of binding socket for nodejs HTTP client request (for discussion only)

httpclnt03.js

//  One shot request HTTP client - show local/remote addresses
//
//  Attempt to use a modified Agent that has own self.createConnection()
//  that binds the client socket to a particular address.

var assert  = require('assert'),
    dns     = require('dns'),
    http    = require('http'),
    net     = require('net'),
    util    = require('util');

function ltrc() { console.log.apply(this, arguments); }


//-  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -

var host_port = 5439;
var host_host = '192.168.57.162';
    host_host = 'tlsf16a';
    host_host = '127.0.0.1';
  //host_host = 'localhost';

var clnt_host = '192.168.57.162';   // works
  //clnt_host = 'tlsf16a';          // forced to 127.0.0.1  does not work !?!
  //clnt_host = '127.0.0.1';        // works
  //clnt_host = 'localhost';        // works? is 127.0.0.1
  //clnt_host = 'localhost4';       // works? is 127.0.0.1
  //clnt_host = 'freakout';         // forced to 127.0.0.1  !!
// Apparently net._createServerHandle(clnt_host) cannot accept a host name
// which would need to be resolved - only IP addresses are acceptable?


//- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// An alternate for http.Agent, which however merely sets its own
// implementation of self.createConnection() in order to force a
// particular binding for the client socket.

function bindingAgent(options) {
  http.Agent.call(this, options);
  // We are changing only this one property of Agent
  this.createConnection = bindingCreateConnection;
}
util.inherits(bindingAgent, http.Agent);

function bindingCreateConnection(port, host, options) {
  ltrc('  bindingCreateConnection(%j,%j,%j) called....', port, host, options);

  ltrc('    binding new client socket to %j', clnt_host);
  var socket;
  socket = new net.Socket({ handle: net._createServerHandle(clnt_host)});
  socket.connect(port, host);
  
  socket.marker_of_insanity = 'hiya';

  return socket;
}

var optionsAgent  = {};
var ourBindingAgent = new bindingAgent(optionsAgent);


//-  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -

var options = { 'host': host_host, 'port': host_port };

// >>>>  Set to true to enable our experiment with alternate realities  <<<<
if (1) {
  options.agent = ourBindingAgent;
}

var creq = http.get(options);

creq.on('response', function (res) {

  var socket = creq.connection;
  if (socket) {
    var host_bound_addr = { 'address': socket.remoteAddress,
                            'port':    socket.remotePort };
    ltrc('  Server address  %j', host_bound_addr );
    var clnt_bound_addr = socket.address();
    ltrc('  Client address  %j', clnt_bound_addr );

    ltrc('    (insanity:  %j )', socket.marker_of_insanity ? 'yes' : 'no');
  }

  ltrc('  Resp  STATUS:   %j', res.statusCode);

  var headers = res.headers;
  var keys = Object.keys(headers);
  ltrc('    HEADERS:  (%d)', keys.length);
  for( var idx=0, l=keys.length; idx < l ; idx++) {
    var key = keys[idx];
    ltrc('      %j    %j', key, headers[key]);
  }

  res.setEncoding('utf8');
  res.on('data', function (chunk) {
    ltrc('    DATA:     %j', chunk);
  });
});

creq.on('error', function (err) {
  ltrc('  Resp  ERROR:   %j', err.message);
});

// vim:ft=javascript:ts=2:sw=2:et:is:hls:ss=10:tw=160:

httpsrvr01.js

// Simple HTTP server just for testing

var assert  = require('assert'),
    dns     = require('dns'),
    http    = require('http'),
    util    = require('util');


function ltrc() { console.log.apply(this, arguments); }


/-  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -

var our_port  = 5439;
var our_host  = '192.168.57.162';
    our_host  = 'tlsf16a';
    our_host  = '127.0.0.1';
    our_host  = 'localhost';

//- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

// Create a server just to dump information about requests

function onRequest(req, res) {
  var socket = req.connection;

  var host_bound_addr = socket.address();
  ltrc('\nHTTP request to   %j', host_bound_addr );
  var clnt_bound_addr = { 'address': socket.remoteAddress,
                          'port':    socket.remotePort };
  ltrc('HTTP request from %j', clnt_bound_addr );

  var headers = req.headers;
  var keys = Object.keys(headers);
  ltrc('\nHTTP request headers:  (%j)', keys.length );
  for( var idx=0, l=keys.length; idx < l ; idx++) {
    var key = keys[idx];
    ltrc('    %j    %j', key, headers[key]);
  }

  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('okay');
}

var hsrvr = http.createServer(onRequest);

function onListening() {
  var srvr  = this;
  var host_bound_addr = srvr.address();
  ltrc('HTTP server is listening on %j', host_bound_addr );
}

hsrvr.listen(our_port, our_host, onListening);

// vim:ft=javascript:ts=2:sw=2:et:is:hls:ss=10:tw=160:

test outputs.txt

Using normal http.Agent that does nothing regarding socket binding:

      [Tom@tlsf16a testing]$ ../node063 httpclnt03.js
        Server address  {"address":"127.0.0.1","port":5439}
  >>>>  Client address  {"port":45146,"family":2,"address":"127.0.0.1"}
          (insanity:  "no" )
        Resp  STATUS:   200
          HEADERS:  (3)
            "content-type"    "text/plain"
            "connection"    "keep-alive"
            "transfer-encoding"    "chunked"
          DATA:     "okay"


Using own Agent that forces client binding:

      [Tom@tlsf16a testing]$ ../node063 httpclnt03.js
        bindingCreateConnection(5439,"127.0.0.1",{}) called....
          binding new client socket to "192.168.57.162"
        Server address  {"address":"127.0.0.1","port":5439}
  >>>>  Client address  {"port":50797,"family":2,"address":"192.168.57.162"}
          (insanity:  "yes" )
        Resp  STATUS:   200
          HEADERS:  (3)
            "content-type"    "text/plain"
            "connection"    "keep-alive"
            "transfer-encoding"    "chunked"
          DATA:     "okay"