TablePCControl/main.cpp

#include "secret.h"
#include <alsa/asoundlib.h>
#include <arpa/inet.h>
#include <array>
#include <cerrno>
#include <codecvt>
#include <csignal>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <fcntl.h>
#include <fstream>
#include <iostream>
#include <memory>
#include <netdb.h>
#include <netinet/in.h>
#include <sched.h>
#include <stdexcept>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <unistd.h>

#define PORT 54321

int serverSocket;

void safe_exit(int code) {

  std::clog << "Exiting\n";

  close(serverSocket);
  exit(code);
}

int get_volume(const char *selem_name) {
  long min, max, volume;
  snd_mixer_t *handle;
  snd_mixer_selem_id_t *sid;

  // Open mixer
  snd_mixer_open(&handle, 0);
  snd_mixer_attach(handle,
                   "default"); // Use "default" for the default sound card
  snd_mixer_selem_register(handle, NULL, NULL);
  snd_mixer_load(handle);

  // Allocate and set mixer element ID
  snd_mixer_selem_id_alloca(&sid);
  snd_mixer_selem_id_set_name(sid, selem_name);

  // Find the mixer element
  snd_mixer_elem_t *elem = snd_mixer_find_selem(handle, sid);

  int volume_percent;
  if (elem) {
    // Get the playback volume range
    snd_mixer_selem_get_playback_volume_range(elem, &min, &max);

    // Get the current playback volume for front left channel
    snd_mixer_selem_get_playback_volume(elem, SND_MIXER_SCHN_FRONT_LEFT,
                                        &volume);

    // Calculate the volume percentage
    volume_percent = (volume - min) * 100 / (max - min);

  } else {
    std::cerr << "Mixer element not found\n";
    snd_mixer_close(handle);
    safe_exit(ENODEV);
  }

  // Clean up
  snd_mixer_close(handle);
  return volume_percent;
}

int main(int argc, char *argv[]) {

  // signal handlers
  signal(SIGTERM, safe_exit);
  signal(SIGINT, safe_exit);
  signal(SIGQUIT, safe_exit);
  signal(SIGHUP, safe_exit);

  // error signal handlers
  signal(SIGSEGV, safe_exit);

  // creating socket
  serverSocket = socket(AF_INET, SOCK_STREAM, 0);

  // specifying the address
  sockaddr_in serverAddress;
  serverAddress.sin_family = AF_INET;
  serverAddress.sin_port = htons(PORT);
  serverAddress.sin_addr.s_addr = INADDR_ANY;

  // binding socket.
  while (bind(serverSocket, (struct sockaddr *)&serverAddress,
              sizeof(serverAddress)) != 0) {
    std::cerr << "error binding socket retring\n";
    sleep(2);
  }

  // listening to the assigned socket
  listen(serverSocket, 5);

accept_new_connection:
  // accepting connection request
  int clientSocket = accept(serverSocket, nullptr, nullptr);

  pid_t pid;
  pid = fork();

  if (pid == -1) {
    std::cerr << "Fork failed";
    safe_exit(-1);

  } else if (pid == 0) {
    // child process
    signal(SIGUSR1, exit);
    char bufferSend[1024];
    int volume_percent = INTMAX_MIN;
    int volume_percent_old;
    while (1) {
      volume_percent_old = volume_percent;
      volume_percent = get_volume("Master");
      if (volume_percent != volume_percent_old) {
      }
      usleep(100000);
      sprintf(bufferSend, "Volume: %d%%\n", get_volume("Master"));
      if (send(clientSocket, bufferSend, strlen(bufferSend), 0) == -1) {
        std::cerr << "send() returned an error code\n";
        safe_exit(-1);
      }
      sleep(1);
    }

  } else {
    // parent process
    char bufferRecv[1024];
    // recieving data
    while (1) {
      memset(&bufferRecv, 0, sizeof(bufferRecv));
      int RecvRetVal = recv(clientSocket, bufferRecv, sizeof(bufferRecv), 0);
      if (RecvRetVal > sizeof(bufferRecv) || RecvRetVal < 0) {
        std::cerr << "recv() returned an error code\n";
        safe_exit(RecvRetVal);
      } else if (RecvRetVal == 0) {
        // detect if client disconected
        kill(pid, SIGUSR1);
        close(clientSocket);
        goto accept_new_connection;
      }

      std::cout << "Message from client: " << bufferRecv << std::endl;
    }

    // closing the socket.
    close(serverSocket);
  }

  return 0;
}