error while sending data to tcp port using tcp tunneling using ngrok

Question

I want to sent a TCP data to a port which was exposed globally. I have written a server code:

server.js

const net = require('net');
const port = 8080;
const host = '127.0.0.1';
var fs = require("fs");

const server = net.createServer();
server.listen(port, host, () => {
    console.log('TCP Server is running on port ' + port + '.');
});

let sockets = [];

fs.writeFile('tcpdata.log', 'id,pm25,pm10,temp,hum,atm,loc,m1,m2,m3,m4,m5,m6,m7,m8,m9,m10.m11,m12,m13,m14,m15,m16\n', function (err) {
  if (err) throw err;
  console.log('Created successfully.');
});

server.on('connection', function(sock) {
    console.log('CONNECTED: ' + sock.remoteAddress + ':' + sock.remotePort);

    sockets.push(sock);

    sock.on('data', function(data) {
        console.log('DATA ' + sock.remoteAddress + ': ' + data);
        fs.appendFile('tcpdata.log', data, function(error){console.log('data written');});
        // Write the data back to all the connected, the client will receive it as data from the server
        sockets.forEach(function(sock, index, array) {
            sock.write(sock.remoteAddress + ':' + sock.remotePort + " said " + data + '\n');
        });
    });

    // Add a 'close' event handler to this instance of socket
    sock.on('close', function(data) {
        let index = sockets.findIndex(function(o) {
            return o.remoteAddress === sock.remoteAddress && o.remotePort === sock.remotePort;
        })
        if (index !== -1) sockets.splice(index, 1);
        console.log('CLOSED: ' + sock.remoteAddress + ' ' + sock.remotePort);
    });
});

Steps followed to send data to TCP port.

1. started the server.js

2. Connect to tcp port 8080

3. AT Commands to send data to tcp port "2.tcp.ngrok.io:16185"

   AT+CREG=1

   OK

   AT+CREG?

   +CREG: 1

   AT+GPS=1

   OK

   AT+CGATT=1

   +CGATT:1

   OK

   AT+CGDCONT=1,"IP","pinternet.interkom.de"

   OK

   AT+CGACT=1,1

   OK

   AT+CIPSTART="TCP","2.tcp.ngrok.io",16185

   CONNECT OK

   OK

   AT+CIPSEND=101,"'A1',22.00,31.00,7.00,15.00,0.00,$GNGGA,170219.094,4900.5489,N,00825.5612,E,0,3,,311.5,M,47.9,M,,*51"

   OK

   AT+CIPSTART="TCP","2.tcp.ngrok.io",16185

   ALREAY CONNECT

   OK

   AT+CIPSEND=101,"'A1',23.00,33.00,6.00,14.00,1.00,$GNGGA,170230.000,4900.5372,N,00825.4908,E,0,4,,227.4,M,47.9,M,,*53"

   OK

4. Usually the data is sent without errors, but there some unkown trash data appearing on tcp port. And there are some close of ports. Can I fixed this unexpected close ups and trash data apearing on the tcp port. Is my code right?

5. Usuall data reception:

6. Unexpected Errors and Closure on TCP ports

events.js:353
      throw er; // Unhandled 'error' event

or

data written
CONNECTED: 127.0.0.1:58072
DATA 127.0.0.1: SSH-2.0-Renci.SshNet.SshClient.0.0.1

or

Can you please help getting this fixed. How can I avoid un-expected tcp connection closure or avoid trash data.

Answer 1

1. I think you should also listen to error event
2. You assume that the on('data') handler, on a given event, handles exactly one command/line? If so, then that's not always the case: you might get partial data, or more than a single command. If newline character (\n) is your delimiter, then you should use a local variable to buffer the input until you get this delimiter and then treat the buffered data as a single line.