//
// youtube -->  https://www.youtube.com/watch?v=x0txsOUhfnQ
//
// tcp server side for orange pi zero 3
// turn on led when LEDON message is received
// turn off led when LEDOF message is received
// uses gpiod library
// sudo apt-get install -y libgpiod-dev
// compiling... sudo gcc this_program.c -lgpiod
// assumes led is connected to pc10 of orange pi zero 3
// pc10 is gpio 74, in orange pi zero 3
//   do sudo gpio readall to find 74 next to PC10
//
#include <netinet/in.h>
#include <gpiod.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <unistd.h>

#define PORT 8080
#ifndef CONSUMER
#define CONSUMER "Consumer"
#endif

int main(int argc, char const* argv[]){
  int server_fd, new_socket;
  ssize_t valread;
  struct sockaddr_in address;
  int opt = 1;
  socklen_t addrlen = sizeof(address);
  char buffer[10] = {0};
  char *chipname = "gpiochip0";
  unsigned int line_num = 74;
  unsigned int val;
  struct gpiod_chip *chip;
  struct gpiod_line *line;
  int i, ret;
  
  chip=gpiod_chip_open_by_name(chipname);
  line=gpiod_chip_get_line(chip, line_num);
  ret=gpiod_line_request_output(line, CONSUMER, 0);
  val=0;
  
  // create socket file descriptor
  if((server_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
    perror("socket failed"); exit(EXIT_FAILURE);}
    
  // forcefully  attaching socket to port 8080
  if(setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))){
    perror("setsockopt"); exit(EXIT_FAILURE);}
    
  address.sin_family=AF_INET;
  address.sin_addr.s_addr=INADDR_ANY;
  address.sin_port=htons(PORT);
  
  // forcefully attaching socket to the port 8080
  if(bind(server_fd, (struct sockaddr*)&address, sizeof(address)) < 0){
    perror("bind failed"); exit(EXIT_FAILURE);}
    
  if(listen(server_fd, 3) < 0){
    perror("listen"); exit(EXIT_FAILURE);}
    
  if((new_socket = accept(server_fd, (struct sockaddr*)&address, &addrlen)) < 0){
    perror("accept"); exit(EXIT_FAILURE);}
    
  while(1){
    valread=read(new_socket, buffer, 10 - 1); // subtract 1 for null terminator at the end
    if(strncmp(buffer, "LEDON", 5) == 0) gpiod_line_set_value(line, val);
    else if(strncmp(buffer, "LEDOF", 5) == 0) gpiod_line_set_value(line, !val);}
    
  close(new_socket); close(server_fd); return 0;}
  
//  
// flutter app to blink led on orange pi zero 3
//
//
// tcp client in flutter
//

import 'package:flutter/material.dart';
import 'dart:io';
import 'dart:async';

late Socket s;

TextStyle myStyle = TextStyle(fontWeight:FontWeight.bold,
fontSize:24);

void main() {runApp(MaterialApp(home:MainScreen(),
theme:ThemeData(scaffoldBackgroundColor:Colors.teal[100])));}

class MainScreen extends StatelessWidget{

void send(val) async {s.writeln(val);}

void connect() async {
print('connecting...');
s=await Socket.connect('192.168.6.106',8080);
s.listen((data){},
onDone:(){},
onError:(e){});
print('connected');}

@override Widget build(c){
return Scaffold(appBar:AppBar(title:Text('tcp client demo')),body:Column(children:[
  SizedBox(height:50),
  ElevatedButton(child:Text('connect',style:myStyle), onPressed:connect),
  SizedBox(height:50),
  ElevatedButton(child:Text('led off',style:myStyle), onPressed:()=>send('LEDON')),
  SizedBox(height:50),
  ElevatedButton(child:Text('led on',style:myStyle), onPressed:()=>send('LEDOFF'))]));}}