#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>

int main(void){
  int tx_socket, rx_socket;
  struct sockaddr_in tx_server_addr, tx_client_addr, rx_addr;
  char client_message[2000];
  char server_response[2000];
  int tx_server_struct_length = sizeof(tx_server_addr);
  int tx_client_struct_length = sizeof(tx_client_addr);
  int rx_struct_length = sizeof(rx_addr);

  // Clean buffers:
  memset(server_response, '\0', sizeof(server_response));
  memset(client_message, '\0', sizeof(client_message));

  // Create tx UDP socket:
  tx_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

  if(tx_socket < 0){
    printf("Error while creating socket\n");
    return -1;
  }
  printf("Socket created successfully\n");



  // Set client port:
  tx_client_addr.sin_family = AF_INET;
  tx_client_addr.sin_port = htons(7789);
  tx_client_addr.sin_addr.s_addr = INADDR_ANY;

  // Bind to the set client port:
  if(bind(tx_socket, (struct sockaddr*)&tx_client_addr, sizeof(tx_client_addr)) < 0){
    printf("Couldn't bind to the port\n");
    printf("Did you set the ip with $ sudo ip addr add 192.168.3.1/24 dev enp5s0");
    return -1;
  }


  // tx message:
  client_message[0] = '\0'; // empty frame, just to trigger the reponse

  // tx port and ip:
  tx_server_addr.sin_family = AF_INET;
  tx_server_addr.sin_port = htons(7789);
  tx_server_addr.sin_addr.s_addr = inet_addr("192.168.3.10");


  // send frame
  if (sendto(tx_socket, client_message, strlen(client_message), 0, (struct sockaddr*)&tx_server_addr, tx_server_struct_length) < 0){
    printf("Can't send\n");
    return -1;
  } else {
    printf("empty UDP frame send\n");
  }




  // Create rx UDP socket:
  rx_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

  rx_addr.sin_family = AF_INET;
  rx_addr.sin_port = htons(7789);
  rx_addr.sin_addr.s_addr = INADDR_ANY;


  // Receive server response:
  int rx_err = 0;
  rx_err = recvfrom(rx_socket, server_response, sizeof(server_response), 0, (struct sockaddr*)&rx_addr, &rx_struct_length);

  if ( rx_err ) {
      printf("Couldn't receive, err = %i", rx_err);
      return -1;
  }

  printf("Received message from IP: %s\n", inet_ntoa(rx_addr.sin_addr));
  printf("Msg from client: %s\n", server_response);




  // Close the socket:
  close(tx_socket);
  close(rx_socket);

  return 0;
}