Trying to send sensor values using an ESP8266 (Wemos D1 R2) to a fastAPI webserver, returns response code -1)

[exxodia]

I want to use an ESP8266 as station(?) to forward detected sensor values to a webserver to be displayed in a browser via fastAPI. The fastAPI code is working fine, and the program for the Wemos D1 is doing good as well. I've tried several Wemos D1 R2 boards and a mini to no avail.

Wemos code:

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <WiFiClient.h>

// Wi-Fi Credentials
const char* ssid = "LTE-WiFi_NTEK";
const char* password = "Ntek12345";


void setup() {
    Serial.begin(115200);
    WiFi.begin(ssid, password);

    Serial.print("Connecting to WiFi...");
    while (WiFi.status() != WL_CONNECTED) {
        delay(1000);
        Serial.print(".");
    }
    Serial.println(" Connected!");
}

void loop() {
    // Call your device-specific function here
    sendDeviceAData();
    sendDeviceBData();
    sendDeviceCData();
    
    delay(5000);  // Send data every 5 seconds
}

void sendDeviceAData() {
    // DHT Sensor
    if (WiFi.status() == WL_CONNECTED) {
        HTTPClient http;
        WiFiClient client;
        http.begin(client,"http://127.0.0.1:8000/deviceA");
        http.addHeader("Content-Type", "application/json");

        // Simulated water level value
        float Temperature = 12.4;
        float Moisture = 12.4;

        String payload = "{\"temperature\": " + String(Temperature) + " \"moisture\": " + String(Moisture) + "}";

        int httpResponseCode = http.POST(payload);

        Serial.println("Device A Data Sent");
        Serial.println(payload);
        Serial.println("Response Code: " + String(httpResponseCode));

        http.end();
    }
}

void sendDeviceBData() {
    // Soil Moisture Sensor
    if (WiFi.status() == WL_CONNECTED) {
        HTTPClient http;
        WiFiClient client;
        http.begin(client, "http://127.0.0.1:8000/deviceB");
        http.addHeader("Content-Type", "application/json");

        // Simulated water level value
        float soilMoisture = 12.4;

        String payload = "{\"soil_moisture\": " + String(soilMoisture) + "}";

        int httpResponseCode = http.POST(payload);

        Serial.println("Device B Data Sent");
        Serial.println(payload);
        Serial.println("Response Code: " + String(httpResponseCode));

        http.end();
    }
}

void sendDeviceCData() {
    // Ultrasonic Sensor for water level
    if (WiFi.status() == WL_CONNECTED) {
        HTTPClient http;
        WiFiClient client;
        http.begin(client, "http://127.0.0.1:8000/deviceC");
        http.addHeader("Content-Type", "application/json");

        // Simulated water level value
        float waterLevel = 12.4;

        String payload = "{\"water_level\": " + String(waterLevel) + "}";

        int httpResponseCode = http.POST(payload);

        Serial.println("Device C Data Sent");
        Serial.println(payload);
        Serial.println("Response Code: " + String(httpResponseCode));

        http.end();
    }
}

fastAPI code:

from fastapi import FastAPI
from pydantic import BaseModel
from typing import List

app = FastAPI()

# In-memory storage for received weather data
data_storage = {
    "deviceA": [],
    "deviceB": [],
    "deviceC": []
}

# Request models for each device
class DeviceAData(BaseModel):
    temperature: float
    moisture: float

class DeviceBData(BaseModel):
    soil_moisture: float

class DeviceCData(BaseModel):
    water_level: float

@app.get("/")
def root():
    return {"message": "Weather Data API is running"}

# Endpoint to receive data from Device A
@app.post("/deviceA")
def receive_device_a_data(data: DeviceAData):
    data_storage["deviceA"].append(data)
    return {"message": "Device A data received", "data": data}

# Endpoint to receive data from Device B
@app.post("/deviceB")
def receive_device_b_data(data: DeviceBData):
    data_storage["deviceB"].append(data)
    return {"message": "Device B data received", "data": data}

# Endpoint to receive data from Device C
@app.post("/deviceC")
def receive_device_c_data(data: DeviceCData):
    data_storage["deviceC"].append(data)
    return {"message": "Device C data received", "data": data}

# Endpoint to retrieve all stored weather data
@app.get("/data")
def get_all_data():
    return data_storage

When the ESP8266 sends data automatically to the webserver, it gives a response code of -1, which according to the library means that connection has failed, yet I have checked by printing WiFi.status() that it is indeed connected. I am not sure about http.begin as I am not familiar with its functions. Could you help me with my problem?

Thank you!