Create a proxy in Node.js

You can create an agent instance in Node.js using the new Agent() method. The http.request() method creates a custom http.Agent instance using the globalAgent from the "http" module.

Syntax

new Agent({options})

Parameters

The above function can accept the following parameters−

• options – These options will contain configurable options that can be set on the agent at creation time. Following are the fields/options a proxy can have -

  • keepAlive - This method keeps the socket whether it has any outstanding requests or not, but retains them to For use by any future requests without actually re-establishing the TCP connection. This connection can be closed using Close Connection. Default value: false.

  • keepAliveMsecs - This option defines the initial delay for TCP keep-Alive packets when the keepAlive option is set to true. The default value is 1000.

  • maxSockets - This option defines the maximum number of sockets allowed per host. By default, this value is infinity.

  • maxTotalSockets – The total number of sockets allowed for all hosts. Each request uses a new socket until the limit is reached. The default value is infinity.

  • maxFreeSockets - This is the maximum number of free sockets that can be kept open in the idle state. The default value is: 256.

  • Scheduling - This is the scheduling policy that can be applied when selecting the next free socket to use. Schedule can be "fifo" or "lifo".

  • Timeout - Represents the socket timeout in milliseconds.

Example

Create a file called agent.js and copy the following code snippet. After creating the file, run this code using the following command as shown in the example below -

node agent.js

agent.js

Live Demo

// Node.js program to demonstrate the creation of new Agent

// Importing the http module
const http = require('http');

// Creating a new agent
var agent = new http.Agent({});

// Defining options for agent
const aliveAgent = new http.Agent({
   keepAlive: true, maxSockets: 5,
});

// Creating connection with alive agent
var aliveConnection = aliveAgent.createConnection;

// Creating new connection
var connection = agent.createConnection;

// Printing the connection
console.log('Succesfully created connection with agent: ',
connection.toString);
console.log('Succesfully created connection with alive agent: ',
aliveConnection.toString);

Output

C:\homeode>> node agent.js
Succesfully created connection with agent: function toString() { [native code] }
Succesfully created connection with alive agent: function toString() { [native code] }

Example

The "agentkeepalive" module provides better flexibility when trying to create sockets or agents. We will use this module in the following examples for better understanding.

Installation

npm install agentkeepalive --save

Program code

// Node.js program to demonstrate the creation of new Agent

// Importing the http module
const http = require('http');
// Importing the agentkeepalive module
const Agent = require('agentkeepalive');

// Creating a new agent
const keepAliveAgent = new Agent({});

// Implementing some options
const options = {
   host: 'tutorialspoint.com',
   port: 80,
   path: '/',
   method: 'GET',
   agent: keepAliveAgent,
};

// Requesting details via http server module
const req = http.request(options, (res) => {
   // Printing statuscode, headers and other details
   // received from the request
   console.log("StatusCode: ", res.statusCode);
   console.log("Headers: ", res.headers);
});

// Printing the agent options
console.log("Agent Options: ", req.agent.options);
req.end();

Output

C:\homeode>> node agent.js
Agent Options: { socketActiveTTL: 0,
   timeout: 30000,
   freeSocketTimeout: 15000,
   keepAlive: true,
   path: null }
StatusCode: 403
Headers: { date: 'Sun, 25 Apr 2021 08:21:14 GMT',
   server: 'Apache',
   'x-frame-options': 'SAMEORIGIN',
   'last-modified': 'Thu, 16 Oct 2014 13:20:58 GMT',
   etag: '"1321-5058a1e728280"',
   'accept-ranges': 'bytes',
   'content-length': '4897',
   'x-xss-protection': '1; mode=block',
   vary: 'User-Agent',
   'keep-alive': 'timeout=5, max=100',
   connection: 'Keep-Alive',
   'content-type': 'text/html; charset=UTF-8' }

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