Huzzah Feather ESP8266 with MAX3232 as RS232 to wifi device

/*
 * Use an ESP8266 Huzzah Feather and MAX3232 board from MikroE to communicate with an RS232 device 
 * (a Dylos DC1700 particulates monitor here, but could be anything) 
 * 
 * This board has only one UART; Pins labelled Rx and Tx are shared with the USB port, so we have to use SoftwareSerial.
 * We choose pins 4 and 5 because they are the only two available that have no standard use for other things.
 * (ESP32 has 3 separate UARTs and would have been easier).
 * The MAX3232 should be soldered to +3 V, GND and pins 4 and 5 (opposite corner to the power pins). 
 * I checked extensively: what the MAX3232 calls Rx is the channel that *transmits* to the remote device; 
 * what it labels as Tx is the channel that receives from the other device. In other words, they are named
 * as labelled on the other device. A null modem cable is needed from MAX3232 to Dylos (with Rx and Tx crossed).
 * You connect Huzzah Feather Tx = pin 4 to Tx on the MAX3232; Huzzah Feather Rx = pin 5 to Rx on the MAX3232.
 */
#include <SoftwareSerial.h>
const byte txPin = 4;
const byte rxPin = 5;
SoftwareSerial max3232(rxPin, txPin);
  
void setup() {

  Serial.begin(9600L);

  pinMode(txPin, OUTPUT);
  pinMode(rxPin, INPUT);

  max3232.begin(9600);
  
  while (!max3232.isListening()) {
    Serial.println("Waiting for MAX3232 to start listening...");
    delay(1000);
  }
  Serial.println("Good, MAX3232 is listening");

}


void loop() {

  Serial.println("Waiting for data on Dylos");

  for (int loops = 0; loops < 120; ++loops) {
    if (max3232.available()) break;
    delay(1000);
  }

  char result[100] = "-1, -1";
  if (max3232.available()) {
    Serial.println("reading Max3232...");
    int i = 0;
    while (max3232.available()) {
      result[i++] = max3232.read();
    }
    result[i] = '\n'; // Just to check it is terminated
  }
  else {
    Serial.println("Timed out");
  }
  
  Serial.println(result);
  
}