request.js

// >>>> code below <<<<

var request = require('request');
request({
  url: 'http://192.168.4.1',
  body: JSON.stringify({
    a: "c",
    b: "d"
  })
}, function (error, response, body) {
  console.log("Got Response");
  console.log(error, response, body);
});

// >>>> result below <<<<

{ Error: Parse Error
    at Error (native)
    at Socket.socketOnData (_http_client.js:363:20)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:176:18)
    at Socket.Readable.push (_stream_readable.js:134:10)
    at TCP.onread (net.js:548:20) bytesParsed: 128, code: 'HPE_INVALID_HEADER_TOKEN' } undefined undefined

// >>>> actual tcp reply
/*
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Connection: close
Server: air quality egg
Content-Length: 41
{"error":"xxxxxxxxxxxxxxxxxxxxxxxxxxxxx"}
*/

// >>>> using curl
/*
> curl 192.168.4.1 -v -d '{"a": "c", "b": "d"}'
* Rebuilt URL to: 192.168.4.1/
*   Trying 192.168.4.1...
* Connected to 192.168.4.1 (192.168.4.1) port 80 (#0)
> POST / HTTP/1.1
> Host: 192.168.4.1
> User-Agent: curl/7.47.0
> Accept: */*
> Content-Length: 20
> Content-Type: application/x-www-form-urlencoded
> 
* upload completely sent off: 20 out of 20 bytes
< HTTP/1.1 200 OK
< Content-Type: application/json; charset=utf-8
< Connection: close
< Server: air quality egg
< Content-Length: 41

*/