• November 28, 2023

Node Js Http Proxy Example

A full-featured http proxy for node.js – GitHub

node–proxy is an HTTP programmable proxying library that supports
websockets. It is suitable for implementing components such as reverse
proxies and load balancers.
Table of Contents
Upgrading from 0. 8. x?
Core Concept
Use Cases
Setup a basic stand-alone proxy server
Setup a stand-alone proxy server with custom server logic
Setup a stand-alone proxy server with proxy request header re-writing
Modify a response from a proxied server
Setup a stand-alone proxy server with latency
Proxying WebSockets
Listening for proxy events
ProxyTable API
Contributing and Issues
npm install -proxy –save
Back to top
Click here
A new proxy is created by calling createProxyServer and passing
an options object as argument (valid properties are available here)
var Proxy = require(‘-proxy’);
var proxy = eateProxyServer(options); // See (†)
†Unless listen(.. ) is invoked on the object, this does not create a webserver. See below.
An object will be returned with four methods:
web req, res, [options] (used for proxying regular HTTP(S) requests)
ws req, socket, head, [options] (used for proxying WS(S) requests)
listen port (a function that wraps the object in a webserver, for your convenience)
close [callback] (a function that closes the inner webserver and stops listening on given port)
It is then possible to proxy requests by calling these functions
eateServer(function(req, res) {
(req, res, { target: ”});});
Errors can be listened on either using the Event Emitter API
(‘error’, function(e) {… });
or using the callback API
(req, res, { target: ”}, function(e) {… });
When a request is proxied it follows two different pipelines (available here)
which apply transformations to both the req and res object.
The first pipeline (incoming) is responsible for the creation and manipulation of the stream that connects your client to the target.
The second pipeline (outgoing) is responsible for the creation and manipulation of the stream that, from your target, returns data
to the client.
var = require(”),
Proxy = require(‘-proxy’);
// Create your proxy server and set the target in the options.
eateProxyServer({target:’localhost:9000′})(8000); // See (†)
// Create your target server
eateServer(function (req, res) {
res. writeHead(200, { ‘Content-Type’: ‘text/plain’});
(‘request successfully proxied! ‘ + ‘\n’ + ringify(req. headers, true, 2));
†Invoking listen(.. ) triggers the creation of a web server. Otherwise, just the proxy instance is created.
This example shows how you can proxy a request using your own HTTP server
and also you can put your own logic to handle the request.
// Create a proxy server with custom application logic
var proxy = eateProxyServer({});
// Create your custom server and just call `()` to proxy
// a web request to the target passed in the options
// also you can use `()` to proxy a websockets request
var server = eateServer(function(req, res) {
// You can define here your custom logic to handle the request
// and then proxy the request.
(“listening on port 5050″)
This example shows how you can proxy a request using your own HTTP server that
modifies the outgoing proxy request by adding a special header.
// To modify the proxy connection before data is sent, you can listen
// for the ‘proxyReq’ event. When the event is fired, you will receive
// the following arguments:
// (ientRequest proxyReq, comingMessage req,
// rverResponse res, Object options). This mechanism is useful when
// you need to modify the proxy request before the proxy connection
// is made to the target.
(‘proxyReq’, function(proxyReq, req, res, options) {
tHeader(‘X-Special-Proxy-Header’, ‘foobar’);});
(req, res, {
target: ”});});
Sometimes when you have received a HTML/XML document from the server of origin you would like to modify it before forwarding it on.
Harmon allows you to do this in a streaming style so as to keep the pressure on the proxy to a minimum.
// Create a proxy server with latency
var proxy = eateProxyServer();
// Create your server that makes an operation that waits a while
// and then proxies the request
// This simulates an operation that takes 500ms to execute
setTimeout(function () {
target: ‘localhost:9008’});}, 500);})(8008);
(‘request successfully proxied to: ‘ + + ‘\n’ + ringify(req. headers, true, 2));
You can activate the validation of a secure SSL certificate to the target connection (avoid self-signed certs), just set secure: true in the options.
// Create the HTTPS proxy server in front of a HTTP server
target: {
host: ‘localhost’,
port: 9009},
ssl: {
key: adFileSync(”, ‘utf8’),
cert: adFileSync(”, ‘utf8’)}})(8009);
// Create the proxy server listening on port 443
cert: adFileSync(”, ‘utf8’)},
target: ‘localhost:9010’,
secure: true // Depends on your needs, could be false. })(443);
HTTP -> HTTPS (using a PKCS12 client certificate)
// Create an HTTP proxy server with an HTTPS target
protocol: ‘:’,
host: ‘my-domain-name’,
port: 443,
pfx: adFileSync(‘path/to/certificate. p12’),
passphrase: ‘password’, },
changeOrigin: true, })(8000);
You can activate the websocket support for the proxy using ws:true in the options.
// Create a proxy server for websockets
target: ‘wslocalhost:9014’,
ws: true})(8014);
Also you can proxy the websocket requests just calling the ws(req, socket, head) method.
// Setup our server to proxy standard HTTP requests
var proxy = new eateProxyServer({
port: 9015}});
var proxyServer = eateServer(function (req, res) {
(req, res);});
// Listen to the `upgrade` event and proxy the
// WebSocket requests as well.
(‘upgrade’, function (req, socket, head) {
(req, socket, head);});
eateProxyServer supports the following options:
target: url string to be parsed with the url module
forward: url string to be parsed with the url module
agent: object to be passed to (s). request (see Node’s agent and agent objects)
ssl: object to be passed to eateServer()
ws: true/false, if you want to proxy websockets
xfwd: true/false, adds x-forward headers
secure: true/false, if you want to verify the SSL Certs
toProxy: true/false, passes the absolute URL as the path (useful for proxying to proxies)
prependPath: true/false, Default: true – specify whether you want to prepend the target’s path to the proxy path
ignorePath: true/false, Default: false – specify whether you want to ignore the proxy path of the incoming request (note: you will have to append / manually if required).
localAddress: Local interface string to bind for outgoing connections
changeOrigin: true/false, Default: false – changes the origin of the host header to the target URL
preserveHeaderKeyCase: true/false, Default: false – specify whether you want to keep letter case of response header key
auth: Basic authentication i. e. ‘user:password’ to compute an Authorization header.
hostRewrite: rewrites the location hostname on (201/301/302/307/308) redirects.
autoRewrite: rewrites the location host/port on (201/301/302/307/308) redirects based on requested host/port. Default: false.
protocolRewrite: rewrites the location protocol on (201/301/302/307/308) redirects to ” or ”. Default: null.
cookieDomainRewrite: rewrites domain of set-cookie headers. Possible values:
false (default): disable cookie rewriting
String: new domain, for example cookieDomainRewrite: “”. To remove the domain, use cookieDomainRewrite: “”.
Object: mapping of domains to new domains, use “*” to match all domains.
For example keep one domain unchanged, rewrite one domain and remove other domains:
cookieDomainRewrite: {
“”: “”,
“*”: “”}
cookiePathRewrite: rewrites path of set-cookie headers. Possible values:
String: new path, for example cookiePathRewrite: “/newPath/”. To remove the path, use cookiePathRewrite: “”. To set path to root use cookiePathRewrite: “/”.
Object: mapping of paths to new paths, use “*” to match all paths.
For example, to keep one path unchanged, rewrite one path and remove other paths:
cookiePathRewrite: {
“/”: “/”,
headers: object with extra headers to be added to target requests.
proxyTimeout: timeout (in millis) for outgoing proxy requests
timeout: timeout (in millis) for incoming requests
followRedirects: true/false, Default: false – specify whether you want to follow redirects
selfHandleResponse true/false, if set to true, none of the webOutgoing passes are called and it’s your responsibility to appropriately return the response by listening and acting on the proxyRes event
buffer: stream of data to send as the request body. Maybe you have some middleware that consumes the request stream before proxying it on e. g. If you read the body of a request into a field called ‘req. rawbody’ you could restream this field in the buffer option:
‘use strict’;
const streamify = require(‘stream-array’);
const HttpProxy = require(‘-proxy’);
const proxy = new HttpProxy();
module. exports = (req, res, next) => {
target: ‘localhost:4003/’,
buffer: streamify(req. rawBody)}, next);};
and are optional.
and rward cannot both be missing
If you are using the method, the following options are also applicable:
error: The error event is emitted if the request to the target fail. We do not do any error handling of messages passed between client and proxy, and messages passed between proxy and target, so it is recommended that you listen on errors and handle them.
proxyReq: This event is emitted before the data is sent. It gives you a chance to alter the proxyReq request object. Applies to “web” connections
proxyReqWs: This event is emitted before the data is sent. Applies to “websocket” connections
proxyRes: This event is emitted if the request to the target got a response.
open: This event is emitted once the proxy websocket was created and piped into the target websocket.
close: This event is emitted once the proxy websocket was closed.
(DEPRECATED) proxySocket: Deprecated in favor of open.
// Error example
// Http Proxy Server with bad target
var proxy = eateServer({
// Listen for the `error` event on `proxy`.
(‘error’, function (err, req, res) {
res. writeHead(500, {
‘Content-Type’: ‘text/plain’});
(‘Something went wrong. And we are reporting a custom error message. ‘);});
// Listen for the `proxyRes` event on `proxy`.
(‘proxyRes’, function (proxyRes, req, res) {
(‘RAW Response from the target’, ringify(proxyRes. headers, true, 2));});
// Listen for the `open` event on `proxy`.
(‘open’, function (proxySocket) {
// listen for messages coming FROM the target here
(‘data’, hybiParseAndLogMessage);});
// Listen for the `close` event on `proxy`.
(‘close’, function (res, socket, head) {
// view disconnected websocket connections
(‘Client disconnected’);});
When testing or running server within another program it may be necessary to close the proxy.
This will stop the proxy from accepting new connections.
port: 1337}});
If you want to handle your own response after receiving the proxyRes, you can do
so with selfHandleResponse. As you can see below, if you use this option, you
are able to intercept and read the proxyRes but you must also make sure to
reply to the res itself otherwise the original client will never receive any
Modify response
var option = {
target: target,
selfHandleResponse: true};
var body = [];
(‘data’, function (chunk) {
(‘end’, function () {
body = (body). toString();
(“res from proxied server:”, body);
(“my response to cli”);});});
(req, res, option);
A proxy table API is available through this add-on module, which lets you define a set of rules to translate matching routes to target routes that the reverse proxy will talk to.
Logo created by Diego Pasquali
Read carefully our Code Of Conduct
Search on Google/Github
If you can’t find anything, open an issue
If you feel comfortable about fixing the issue, fork the repo
Commit to your local branch (which must be different from master)
Submit your Pull Request (be sure to include tests and update documentation)
The MIT License (MIT)
Copyright (c) 2010 – 2016 Charlie Robbins, Jarrett Cruger & the Contributors.
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
Build a Node.js Proxy Server in Under 10 minutes! - Twilio

Build a Node.js Proxy Server in Under 10 minutes! – Twilio

We have all heard the term “proxy”. It might sound like it’s some kind of portal to a new dimension from the Matrix movies, but it turns out it’s very very useful!
In a nutshell, a proxy is an intermediary application which sits between two (or more) services and processes/modifies the requests and responses in both directions. This sounds complicated, I know, but let’s try with a simpler analogy:
Imagine you meet someone from Spain, but you don’t speak Spanish. What do you do? Well, you remember that your friend Santiago knows both Spanish and English and can translate for you.
The process goes like this:
You tell something to Santiago in English
Santiago translates it to Spanish in his head and says it in Spanish to your new friend
Your new friend replies back to Santiago in Spanish
Santiago then translates it in his head and tells you the response in English
Santiago in this case serves as a proxy between you and your new friend. You can’t speak directly to each other but thanks to the translator you can relay messages (i. e. requests and responses) and have a conversation!
Okay, now that we know what a proxy is, what are the use cases for it? Well, here are a few that we, at Twilio, find really useful:
Authorization – Forward only requests that are authorized to access a service
Load balancing – Distribute the requests equally among many instances
Logging – Log every requests going to a Back End API service
And many more…
Now that you know what a proxy is and why it is useful, let’s build a simple one using!
To follow along, you need and Yarn installed, which are available on Mac, Windows and Linux distributions.
Build the simple proxy
In a few easy steps we are going to create a simple proxy in which can forward requests to multiple different servers/endpoints!
The full code which will be implemented step-by-step is available on GitHub here.
Initialize the project
Let’s start by initiating a new node project:
This will generate a file which will contain a basic project configuration. The command will prompt you with multiple questions (name, version, description, etc. ) – you can click ‘Enter’ on all of them to accept the default values (for example, by default the entry point will be).
Install dependencies
We need a few packages to make the proxy work:
express: Minimalist web framework
-proxy-middleware: Simple proxy framework
(optional) morgan – HTTP request logger middleware
which we can install by running:
yarn add express -proxy-middleware morgan
Define a start command
We need to add a start command to our project, so after a small change, your file should look like this (Depending on when you install these packages, some version numbers might differ, but their core functionality should stay the same. If the behaviour is drastically different, check their latest documentations. ):
“name”: “simple-nodejs-proxy”,
“version”: “1. 0. 0”,
“main”: “”,
“license”: “MIT”,
“dependencies”: {
“express”: “^4. 17. 1”,
“-proxy-middleware”: “^1. 5”,
“morgan”: “^1. 10. 0”},
“scripts”: {
“start”: “node “}}
If we now add an empty file, we can execute the project through:
This should run the file. Because the file is empty the console output should also be empty.
But enough configurations, let’s actually proxy some requests!
Create a simple proxy
This is where the interesting bits begin. Go ahead and open the file and add the necessary imports:
const express = require(‘express’);
const morgan = require(“morgan”);
const { createProxyMiddleware} = require(‘-proxy-middleware’);
Now we can create a basic express server and define some constants which we will use later:
// Create Express Server
const app = express();
// Configuration
const PORT = 3000;
const HOST = “localhost”;
const API_SERVICE_URL = “;
Before we implement the proxy logic, we can add the morgan middleware which logs the incoming requests:
// Logging
To be able to test that we proxy only what we want, let’s add a mock /info endpoint which doesn’t forward the request, but rather returns a simple text response:
// Info GET endpoint
(‘/info’, (req, res, next) => {
(‘This is a proxy service which proxies to Billing and Account APIs. ‘);});
Before defining the proxy endpoints, let’s also add a simple authorization/permission handling middleware which sends 403 (Forbidden) if the Authorization Header is missing:
// Authorization
(”, (req, res, next) => {
if (thorization) {
next();} else {
Then we define the proxy endpoint. We want to proxy all requests starting with /json_placeholder to the notorious JSONPlaceholder API (a simple mock API which contains multiple endpoints supporting all HTTP methods). We also define a pathRewrite so that /json_placeholder is omitted when forwarded to the API:
// Proxy endpoints
(‘/json_placeholder’, createProxyMiddleware({
changeOrigin: true,
pathRewrite: {
[`^/json_placeholder`]: ”, }, }));
This way, when we, for example, send a request to localhost:3000/json_placeholder/posts/1, the URL will be rewritten to /posts/1 (in this case:), thus removing /json_placeholder which the API doesn’t need.
And, last but not least, we start the configured server with this function call:
// Start the Proxy
(PORT, HOST, () => {
(`Starting Proxy at ${HOST}:${PORT}`);});
Run the proxy
Let’s start the proxy with the following command:
This prints something along the lines of:
yarn run v1. 22. 4
$ node
[HPM] Proxy created: / -> [HPM] Proxy rewrite rule created: “^/json_placeholder” ~> “”
Starting Proxy at localhost:3000
The proxy should now be running and if we open a second terminal and send a GET request to the /info:
We should receive a response from our proxy. And, unsurprisingly, we get:
This is a proxy service which proxies to JSONPlaceholder API.
Okay, this is great and all, but we don’t want some boring GET endpoints, we want to proxy!
In order to test the proxying, we can send a new GET request like this:
curl localhost:3000/json_placeholder/posts/1
Oh, no! This returns:
Fear not, this is expected because we included the authorization middleware which requires that every request contains an Authorization Header. So, make this small modification (you can even change it to your name because due to the simplicity of our authorization step, every name would work! ):
curl -H “Authorization: nikolay” localhost:3000/json_placeholder/posts/1
This gives us:
“userId”: 1,
“id”: 1,
“title”: “sunt aut facere repellat provident occaecati excepturi optio reprehenderit”,
“body”: “quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto”}
Hooray! Your first successfully proxied request! We can even try this with a POST request:
curl -X POST -H “Authorization: real_user” –data ‘{“title”: “Build a Proxy Server in Under 10 minutes! “, “body”: “We have all heard the term “proxy”… “, userId=”1”}’ localhost:3000/json_placeholder/posts
The POST request works as expected:
“{\”title\””: \””Build a Proxy Server in Under 10 minutes! \””

\””body\””: \””We have all heard the term “”proxy””… \””

userId””: “”\””1\””}””

Frequently Asked Questions about node js http proxy example

Leave a Reply

Your email address will not be published. Required fields are marked *