echoTCP.js

var net = require('net');
var log = require('./logSingleton')();
var redis = require('./redisSingleton')();
var moment = require('moment-timezone');


if (!String.prototype.startsWith) {
    String.prototype.startsWith = function(searchString, position){
        position = position || 0;
        return this.substr(position, searchString.length) === searchString;
    };
}

module.exports.begin = function(port, maxRows, onListen) {
    function rpush(address, payload) {
        redis.RPUSH(address, payload, function(err, length) {
            if (length > maxRows)
                redis.LPOP(address);
        });
    }

    var server = net.createServer({ allowHalfOpen: true }, function(sock) {
        var ended = false;
        var errorSeen = null;
        var remoteAddress = sock.remoteAddress;
        if (remoteAddress.startsWith('::ffff:'))
            remoteAddress = remoteAddress.substr('::ffff:'.length);
        var remotePort = sock.remotePort;
        var when = moment().tz('America/Los_Angeles').format('M/D/YY HH:mm');
        var localFinSent = false;
        var remoteFinSent = false;
        var ascii = '';
        var hex = '';



        var neverSawRemoteFin = false;
        var closedSocketAbnormally = false;
        var sentDataTwice = false;
        var sentDataNever = true;

        setTimeout(function() {
            if (!ended)
            {
                neverSawRemoteFin = true;
                sock.end();
            }
        }, 5000);

        var fullResponse = 'At ' + when + ', TCP payload from ' + remoteAddress + ':' + remotePort;

        sock.on('data', function(message) {
            if (!ended)
            {
                var good = false;

                if (message)
                    good = message.toString().indexOf('\n') < 0;

                if (good && !sentDataTwice)
                {
                    if (sentDataNever)
                    {
                        sock.write(fullResponse);
                        sentDataNever = false;

                        ascii = message.toString().replace(/[\x00-\x1F]/g, "_");
                        hex = message.toString('hex');

                        setTimeout(function() {
                            if (!ended)
                            {
                                response = ' of ' + ascii.length + ' bytes: ';
                                fullResponse += response;
                                sock.write(response);
                            }
                        }, 725);

                        setTimeout(function() {
                            if (!ended)
                            {
                                if (!remoteFinSent)
                                    neverSawRemoteFin = true;

                                response = '"' + ascii + '" [' + hex + ']';
                                fullResponse += response;
                                sock.end(response);
                                localFinSent = true;
                            }
                        }, 1525);
                    }
                    else
                        sentDataTwice = true;
                }
                else
                {
                    log.warn({ body: ascii, ip: remoteAddress, port: remotePort }, "Improper packet");
                }
            }

        });

        sock.on('end', function() {
            remoteFinSent = true;
        });

        sock.on('error', function(error) {
            if (error)
            {
                closedSocketAbnormally = true;
                log.warn({ body: ascii, ip: remoteAddress, port: remotePort, error: error }, "Socket error");
            }
        });

        sock.on('close', function(had_error) {
                if (!localFinSent)
                    closedSocketAbnormally = true;

                if (sentDataNever)
                    fullResponse += "... but client never sent data!";
                else if (closedSocketAbnormally)
                    fullResponse += "... but socket was closed too early!";
                else if (neverSawRemoteFin)
                    fullResponse += "... but socket wasn't shut down properly!";
                else if (sentDataTwice)
                    fullResponse += "... but client sent data more than once!";

                rpush(remoteAddress, fullResponse);
                log.info({ body: ascii, ip: remoteAddress, port: remotePort, response: fullResponse }, "Success");

                ended = true;
            }
        );
    }).listen(port);

    process.nextTick(function() { onListen(); });
}