400 Bad Request on Json POST request

// I do have seen some postings on this topic but didn't found a solution in there.

Hi.

I'm setting up a little project on an esp8266, trying to make a POST request to a Gotify instance, using the bearSSL_CertStore example as boilerplate.

Everything is working great so far (a.k.a. Server connected, GET works fine) but on POST I get an '400 Bad Request' in response.
Should be a problem with the setup of the POST request but I can't figure out what it might be...

Code:

#include <ArduinoJson.h>
#include <ESP8266WiFi.h>
#include <CertStoreBearSSL.h>
#include <time.h>
#include <FS.h>
#include <LittleFS.h>

#ifndef STASSID
#define STASSID "ssid"
#define STAPSK  "pw"
#endif

const char *ssid = STASSID;
const char *pass = STAPSK;
StaticJsonDocument<200> doc;


// A single, global CertStore which can be used by all
// connections.  Needs to stay live the entire time any of
// the WiFiClientBearSSLs are present.
BearSSL::CertStore certStore;

// Set time via NTP, as required for x.509 validation
void setClock() {
  configTime(3 * 3600, 0, "pool.ntp.org", "time.nist.gov");

  Serial.print("Waiting for NTP time sync: ");
  time_t now = time(nullptr);
  while (now < 8 * 3600 * 2) {
    delay(500);
    Serial.print(".");
    now = time(nullptr);
  }
  Serial.println("");
  struct tm timeinfo;
  gmtime_r(&now, &timeinfo);
  Serial.print("Current time: ");
  Serial.print(asctime(&timeinfo));
}

// Try and connect using a WiFiClientBearSSL to specified host:port and make a POST request
void post(BearSSL::WiFiClientSecure *client, const char *host, const uint16_t port, const char *path) {
  if (!path) {
    path = "/";
  }

  Serial.printf("Trying: %s...", host);
  client->connect(host, port);
  if (!client->connected()) {
    Serial.printf("*** Can't connect. ***\n-------\n");
    return;
  }
  Serial.printf("Connected!\n-------\n");


  doc["message"] = "message";
  doc["title"] = "titel";
  doc["priority"] = "5";
  String result;
  serializeJson(doc, result);
  int len1 = measureJson(doc);

  client->write("POST ");
  client->write(path);
  client->write(" HTTP/1.0\r\nHost: ");
  client->write(host);
  client->write("\r\n");
  client->write("Content-Type: application/json\r\n");
  client->write("Content-Length: + len1\r\n");
  client->write("\r\n");
  client->write(result.c_str());
  client->write("\r\n");
  client->write("\r\n");


  Serial.println(len1);
  Serial.println(result);
  Serial.println();

  uint32_t to = millis() + 5000;
  if (client->connected()) {
    do {
      char tmp[64];
      memset(tmp, 0, 64);
      int rlen = client->read((uint8_t*)tmp, sizeof(tmp) - 1);
      yield();
      if (rlen < 0) {
        break;
      }
      Serial.print(tmp);
    } while (millis() < to);
  }
  client->stop();
  Serial.printf("\n-------\n");
}

void setup() {
  Serial.begin(9600);
  Serial.println();
  Serial.println();

  LittleFS.begin();

  // We start by connecting to a WiFi network
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, pass);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");

  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());

  setClock(); // Required for X.509 validation

  int numCerts = certStore.initCertStore(LittleFS, PSTR("/certs.idx"), PSTR("/certs.ar"));
  Serial.printf("Number of CA certs read: %d\n", numCerts);
  if (numCerts == 0) {
    Serial.printf("No certs found. Did you run certs-from-mozilla.py and upload the LittleFS directory before running?\n");
    return; // Can't connect to anything w/o certs!
  }
}

void loop() {

  BearSSL::WiFiClientSecure *bear = new BearSSL::WiFiClientSecure();
  // Integrate the cert store with this connection
  bear->setCertStore(&certStore);
  post(bear, "my.domain", 443, "/gotify/message?token=TokenID");
  delete bear;
  delay(30000);
}

[tt]+ len1[/tt] is not a valid value for the Content-Length header.

Pieter

Wow... :o
You're right.

Changed it from:

  client->write("Content-Length: + len1\r\n");

to

client->write("Content-Length: ");
client->write(len1);
client->write("\r\n");

but now I'm running into a conversion error while using

client->write(len1);
invalid conversion from 'int' to 'const char*' [-fpermissive]

I think this is because of the write() function, already figuered this out with 'result' where I had to use

result.c_str()

to give the right input to write() function

write is for writing bytes, if you want to print an integer as ASCII, use client->print(...).

thx!

Problem solved.

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