Readable stream state (1=true 0=false n=null)

client.js

const net = require('net');

const READABLE = 1;

const client = new net.Socket();
const oldRead = client.read;

let connected = false;

client.on('error', (err) => log('error'));

client.on('close', () =>
{
  log(`close`);
  
  if (connected)
  {
    //console.log(client);
  }
  
  connected = false;
  
  setTimeout(connect, 333);
});

client.on('connect', () =>
{
  log(`connect`);
  
  connected = true;
});

if (READABLE)
  client.on('readable', () =>
  {
    log(`readable`, client.read());
  });
else
  client.on('data', (data) =>
  {
    log(`data`, data);
  });

connect();

setInterval(() => 
{
  if (connected)
  {
    log(`write`);
    client.write(Buffer.from([0, 1, 2]));
  }
}, 1000);

function connect()
{
  log(`connecting`);
  
  client.connect(502, '127.0.0.1');
}

function log(event, data)
{
  console.log(
    `${event.padEnd(10)}: `
    + `readable=${f(client.readable)} `
    + `isPaused()=${f(client.isPaused())} `
    + `reading=${f(client._readableState.reading)} `
    + `flowing=${f(client._readableState.flowing)} `
    + `data=`, data);
}

function f(v)
{
  return v === true ? 1 : v === false ? 0 : v === null ? 'n' : v;
}

log.txt

λ node10.15 client.js
connecting: readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
connect   : readable=1 isPaused()=1 reading=1 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=1 flowing=0 data= undefined
readable  : readable=1 isPaused()=1 reading=1 flowing=0 data= <Buffer 00 01 02>
write     : readable=1 isPaused()=1 reading=1 flowing=0 data= undefined
readable  : readable=1 isPaused()=1 reading=1 flowing=0 data= <Buffer 00 01 02>
write     : readable=1 isPaused()=1 reading=1 flowing=0 data= undefined
readable  : readable=1 isPaused()=1 reading=1 flowing=0 data= <Buffer 00 01 02>
write     : readable=1 isPaused()=1 reading=1 flowing=0 data= undefined
readable  : readable=1 isPaused()=1 reading=1 flowing=0 data= <Buffer 00 01 02>
write     : readable=1 isPaused()=1 reading=1 flowing=0 data= undefined
readable  : readable=1 isPaused()=1 reading=1 flowing=0 data= <Buffer 00 01 02>
write     : readable=1 isPaused()=1 reading=1 flowing=0 data= undefined
readable  : readable=1 isPaused()=1 reading=1 flowing=0 data= <Buffer 00 01 02>
error     : readable=0 isPaused()=1 reading=1 flowing=0 data= undefined
close     : readable=0 isPaused()=1 reading=1 flowing=0 data= undefined
connecting: readable=0 isPaused()=1 reading=1 flowing=0 data= undefined
error     : readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
close     : readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
connecting: readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
error     : readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
close     : readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
connecting: readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
error     : readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
close     : readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
connecting: readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
error     : readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
close     : readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
connecting: readable=0 isPaused()=1 reading=0 flowing=0 data= undefined
connect   : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
write     : readable=1 isPaused()=1 reading=0 flowing=0 data= undefined
^C

λ node10.9 client.js
connecting: readable=0 isPaused()=0 reading=0 flowing=n data= undefined
connect   : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
error     : readable=0 isPaused()=0 reading=1 flowing=n data= undefined
close     : readable=0 isPaused()=0 reading=1 flowing=n data= undefined
connecting: readable=0 isPaused()=0 reading=1 flowing=n data= undefined
error     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
close     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
connecting: readable=0 isPaused()=0 reading=0 flowing=n data= undefined
error     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
close     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
connecting: readable=0 isPaused()=0 reading=0 flowing=n data= undefined
error     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
close     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
connecting: readable=0 isPaused()=0 reading=0 flowing=n data= undefined
error     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
close     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
connecting: readable=0 isPaused()=0 reading=0 flowing=n data= undefined
connect   : readable=1 isPaused()=0 reading=0 flowing=n data= undefined
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
write     : readable=1 isPaused()=0 reading=1 flowing=n data= undefined
readable  : readable=1 isPaused()=0 reading=1 flowing=n data= <Buffer 00 01 02>
error     : readable=0 isPaused()=0 reading=1 flowing=n data= undefined
close     : readable=0 isPaused()=0 reading=1 flowing=n data= undefined
connecting: readable=0 isPaused()=0 reading=1 flowing=n data= undefined
error     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
close     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
connecting: readable=0 isPaused()=0 reading=0 flowing=n data= undefined
error     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
close     : readable=0 isPaused()=0 reading=0 flowing=n data= undefined
connecting: readable=0 isPaused()=0 reading=0 flowing=n data= undefined
^C

server.js

const net = require('net');

const server = net.createServer();

server.on('connection', (conn) =>
{
  console.log('server#connection');
  
  conn.on('error', (err) => console.error('conn#error', err.message));
  conn.on('close', (err) => console.log('conn#close'));
  conn.on('readable', () =>
  {
    const data = conn.read();
    
    if (data)
    {
      console.log('conn#readable', data);
      
      conn.write(data);
    }
  });
});

server.on('error', (err) => console.error(err.message));

server.on('close', () => console.log('server#close'));

server.on('listening', () => console.log('server#listening'));

server.listen(502);