When attempting to use the node.js REPL over a socket, the connection will unexpectedly terminate if the user presses CTRL + C

Question

When attempting to use the node.js REPL over a socket, the connection will unexpectedly terminate if the user presses CTRL + C

As I attempt to utilize REPL over a socket in a manner similar to a telnet connection, I have encountered an issue whereby pressing CTRL + C or CTRL + D, or encountering an error result in the socket connection becoming unresponsive.

The code written in node.js is as follows:

var net = require("net");
var connections = 0;

// Establishing Socket port 5001
net.createServer(function (socket) {
  connections += 1;
  var server = require("repl").start(
      'session:' + connections + ' > ', 
      socket
  );
  server.rli.on('exit', function() {
    socket.end();
  });
}).listen(5001);

// Console
var server = require("repl").start('session:' + (++connections) + ' > ', null);

To implement this, I run the following command in another terminal:

telnet localhost 5001

However, I am facing difficulties. What could be causing this behavior?

node.js sockets read-eval-print-loop

Answer 1

Answer №1

It could be a Linux-related issue.

I decided to experiment with a Telnet server example using Node.js. When testing it on Windows, each key press triggered the receiveData function, but on Linux, this did not happen. In Linux, the processing seemed to occur line by line rather than character by character.

Below is the code snippet I tested:

var net = require('net');
var sockets = [];

/*
 * Removes carriage return and newline characters from input
 */
function cleanInput(data) {
    return data.toString().replace(/(\r\n|\n|\r)/gm,"");
}

/*
 * Executed when data is received from a socket
 */
function receiveData(socket, data) {
    var cleanData = cleanInput(data);
    if(cleanData === "@quit") {
        socket.end('Goodbye!\n');
    }
    else {
        for(var i = 0; i<sockets.length; i++) {
            if (sockets[i] !== socket) {
                sockets[i].write(data);
            }
        }
    }
    socket.write('Data: ' + data);
}

/*
 * Executed when a socket connection ends
 */
function closeSocket(socket) {
    var i = sockets.indexOf(socket);
    if (i != -1) {
        sockets.splice(i, 1);
    }
}

/*
 * Callback method executed when a new TCP socket connection is established
 */
function newSocket(socket) {
    sockets.push(socket);
    socket.write('Welcome to the Telnet server!\n');
    socket.on('data', function(data) {
        receiveData(socket, data);
    })
    socket.on('end', function() {
        closeSocket(socket);
    })
}

// Create a new server instance and specify a callback for handling connections
var server = net.createServer(newSocket);

// Start listening on port 8888
server.listen(8888);

Answer 2

It could be a Linux-related issue.

I decided to experiment with a Telnet server example using Node.js. When testing it on Windows, each key press triggered the receiveData function, but on Linux, this did not happen. In Linux, the processing seemed to occur line by line rather than character by character.

Below is the code snippet I tested:

var net = require('net');
var sockets = [];

/*
 * Removes carriage return and newline characters from input
 */
function cleanInput(data) {
    return data.toString().replace(/(\r\n|\n|\r)/gm,"");
}

/*
 * Executed when data is received from a socket
 */
function receiveData(socket, data) {
    var cleanData = cleanInput(data);
    if(cleanData === "@quit") {
        socket.end('Goodbye!\n');
    }
    else {
        for(var i = 0; i<sockets.length; i++) {
            if (sockets[i] !== socket) {
                sockets[i].write(data);
            }
        }
    }
    socket.write('Data: ' + data);
}

/*
 * Executed when a socket connection ends
 */
function closeSocket(socket) {
    var i = sockets.indexOf(socket);
    if (i != -1) {
        sockets.splice(i, 1);
    }
}

/*
 * Callback method executed when a new TCP socket connection is established
 */
function newSocket(socket) {
    sockets.push(socket);
    socket.write('Welcome to the Telnet server!\n');
    socket.on('data', function(data) {
        receiveData(socket, data);
    })
    socket.on('end', function() {
        closeSocket(socket);
    })
}

// Create a new server instance and specify a callback for handling connections
var server = net.createServer(newSocket);

// Start listening on port 8888
server.listen(8888);

When attempting to use the node.js REPL over a socket, the connection will unexpectedly terminate if the user presses CTRL + C

Answer №1

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