Node.js server.addContext() Method

The server.addContext() is an inbuilt application programming interface of class Socket within tls module which is used to add the security context for the use of the client.

Syntax:

server.addContext(hostname, context)

Parameters: This method takes the following argument as a parameter:

• hostname: A server name indicating hostname.
• context: Any of the properties from the tls.createSecureContext() options arguments.

Return Value: This method does not return any value.

How to generate private keys and public certificates?

Private key: Open Notepad and copy and paste the following key:

-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----

Save the file as a private key.pem

Public certificate: Open Notepad and copy and paste the following key:

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

Save the file as public-cert.pem

Example 1: Filename: index.js

javascript

// Node.js program to demonstrate the
// server.addContext() method

const tls = require('tls'),
    fs = require('fs'),

    // Port and host address for server
    PORT = 1337,
    HOST = '127.0.0.1';

// Private key and public certificate for access
const options = {
    key: fs.readFileSync('private-key.pem'),
    cert: fs.readFileSync('public-cert.pem'),
    rejectUnauthorized: false
};

// Creating and initializing server
const server = tls.createServer(options,
    function (socket) {

        // Print the data that we received
        socket.on("data", function (data) {
            console.log('\nReceived: %s ',
                data.toString().replace(/(\n)/gm, ""));
        });

    });

// Adding context into the server
server.addContext('127.0.0.2', options.key);
console.log("context is added");

// Start listening on a specific
// port and address
server.listen(PORT, HOST, function () {
    console.log("I'm listening at %s, "
        + "on port %s", HOST, PORT);
});

// When an error occurs, show it.
server.on("error", function (error) {

    console.error(error);
    // Close the connection after the
    // error occurred.
    // server.destroy();
});

server.on("end", () => {
    server.end();
    //server.destroy();
})


// Creating and initializing client
const client = tls.connect(PORT, HOST,
    options, function () {

        // Check if the authorization worked
        if (client.authorized) {
            console.log("Connection authorized"
                + " by a Certificate Authority.");
        } else {
            console.log("Connection not authorized: "
                + client.authorizationError)
        }

        // Send a friendly message
        client.write(
            "I am the client sending you a message.");
        client.end();
    });

client.on("close", function () {
    console.log("Connection closed");
});

// When an error occurs, show it.
client.on("error", function (error) {

    console.error(error);

    // Close the connection after
    // the error occurred.
    client.destroy();
});

Output:

context is added
I'm listening at 127.0.0.1, on port 1337
Connection not authorized: DEPTH_ZERO_SELF_SIGNED_CERT

Received: I am the client sending you a message.
Connection closed

Example 2: Filename: index.js

javascript

// Node.js program to demonstrate the
// server.addcontext() method

const tls = require('tls'),
    fs = require('fs'),

    // Port and host address for server
    PORT = 1337,
    HOST = '127.0.0.1';

// Private key and public certificate for access
const options = {
    key: fs.readFileSync('private-key.pem'),
    cert: fs.readFileSync('public-cert.pem'),
    rejectUnauthorized: false
};

// Creating and initializing server
const server = tls.createServer(options,
    function (socket) {

        // Print the data that we received
        socket.on('data', function (data) {
            console.log('\nReceived: %s ',
                data.toString()
                    .replace(/(\n)/gm, ""));
        });
    });

// Adding context into the server
// by using addContext() method
server.addContext('127.0.0.2', options.key);
console.log("context is added");

// Start listening on a specific
// port and address
server.listen(PORT, HOST, function () {
    console.log("I'm listening at %s, "
        + "on port %s", HOST, PORT);
});

// Creating and initializing client
const client = tls.connect(PORT,
    HOST, options, function () {

        // Send a friendly message
        client.write("I am the client "
            + "sending you a message.");
        client.end();
    });

Run the index.js file using the following command:

node index.js

Output:

context is added
I'm listening at 127.0.0.1, on port 1337

Received: I am the client sending you a message.

Reference: https://nodejs.org/dist/latest-v12.x/docs/api/tls.html#tls_server_addcontext_hostname_context