net module: data receiving unreliable?

Hi,

I have a small ESP8266 module which is supposed to receive simple data via simple TCP. The net module should do that and it works mostly:

var server = net.createServer(function(socket) {
  socket.on('data', function(data) {
    try {
      let a=JSON.parse(data);
      console.log(">"+JSON.stringify(a));
    } catch(e) {
      console.log("ERROR: ", e);
    }
  });
  socket.end();
});

server.listen(1234);

On the sender side I do a simple test via netcat:

for i in {0..4} ; do echo "{'toggle':$i}" | nc 192.168.21.105 1234 ; done

But what I get on the Espruino side is:

{"toggle":0}
{"toggle":2}
{"toggle":3}
{"toggle":4}
{"toggle":0}
{"toggle":1}
{"toggle":3}
{"toggle":4}
{"toggle":0}
{"toggle":1}
{"toggle":3}
{"toggle":4}
{"toggle":0}
{"toggle":1}
{"toggle":1}
{"toggle":2}
{"toggle":3}
{"toggle":4}

which is not what I'd expect from TCP. I should see 0, 1, 2, 3, 4.
Even if I send one string at a time (and not 5 in a loop), it gets lost in about 20% of the cases.

Am I doing something wrong? Is the net module on ESP8266 not working reliably?