[SOLVED] ESP01 http request only working for port 80

Turns out the problem was not with the ESP01 or with Espruino, but with my malformed request :) The debugging methods from this thread made that clear (it showed a HTTP-400 header coming back).

For whoever finds it useful, this is how Espruino connects to Home Assistant:

  
  var wifi   = require("Wifi");
  var entity = 'smoke_kitchen';

  wifi.connect("SSID", {password:"PASS"}, function (e) { 
    if( ! e )
    {
      wifi.setHostname("SmokeAlarm-"+entity+"_"+getSerial() );
      
      var http = require("http");
      var data = JSON.stringify( {state:'on'} );
      
      var options = {
        host: 'HASS-HOST',
        port: 8123,
        path: '/api/states/input_boolean.' + entity,
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Content-Length': data.length,
          'x-ha-access': 'Token if needed',
        },
      };
      
      var req = http.request( options, function (res) {
        console.log('Status: ' + res.statusCode);
        console.log( res );
      });
      
      req.write( data );
      req.end();
      
    } else
    { 
      console.log("Error connecting to wifi: ", e );
    }
  });