#include <netdb.h>
#include <netinet/in.h>
#include <pthread.h> /* POSIX Threads */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

void *server_main(void *);
void *client_main(void *);

int main() {
  pthread_t thread1, thread2;

  /* create threads 1 and 2 */
  pthread_create(&thread1, NULL, server_main, (void *)NULL);
  pthread_create(&thread2, NULL, client_main, (void *)NULL);

  /* Main block now waits for both threads to terminate, before it exits
     If main block exits, both threads exit, even if the threads have not
     finished their work */
  pthread_join(thread1, NULL);
  pthread_join(thread2, NULL);

  return 0;
}

void client_error(const char *msg) {
  perror(msg);
  fprintf(stderr, "CLIENT: %s\n", msg);
  fflush(stdout);
  fflush(stderr);
  exit(1);
}

void server_error(const char *msg) {
  perror(msg);
  fprintf(stderr, "SERVER: %s\n", msg);
  fflush(stdout);
  fflush(stderr);
  exit(1);
}

void *server_main(void *) {
  int sockfd, newsockfd, portno;
  socklen_t clilen;
  char buffer[256];
  sockaddr_in serv_addr, cli_addr;
  int n;
  sockfd = socket(AF_INET, SOCK_STREAM, 0);
  if (sockfd < 0) server_error("ERROR opening socket");
  bzero((char *)&serv_addr, sizeof(serv_addr));
  portno = 11223;
  serv_addr.sin_family = AF_INET;
  serv_addr.sin_addr.s_addr = INADDR_ANY;
  serv_addr.sin_port = htons(portno);
  // Also set the accept socket as reusable
  {
    int flag = 1;
    setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (char *)&flag, sizeof(int));
  }
  if (bind(sockfd, (sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
    server_error("ERROR on binding");
  listen(sockfd, 5);
  clilen = sizeof(cli_addr);
  newsockfd = accept(sockfd, (sockaddr *)&cli_addr, &clilen);
  if (newsockfd < 0) server_error("ERROR on accept");
  bzero(buffer, 256);
  n = read(newsockfd, buffer, 255);
  if (n < 0) server_error("ERROR reading from socket");
  printf("Here is the message: %s\n", buffer);
  if (strcmp(buffer, "Hello World!")) {
    server_error("Data is corrupt");
  }
  n = write(newsockfd, "I got your message", 18);
  if (n < 0) server_error("ERROR writing to socket");
  close(newsockfd);
  close(sockfd);
  return 0;
}

void *client_main(void *) {
  int sockfd, portno, n;
  sockaddr_in serv_addr;
  hostent *server;

  char buffer[256];
  portno = 11223;
  sockfd = socket(AF_INET, SOCK_STREAM, 0);
  if (sockfd < 0) client_error("ERROR opening socket");
  server = gethostbyname("localhost");
  if (server == NULL) {
    fprintf(stderr, "ERROR, no such host\n");
    exit(0);
  }
  bzero((char *)&serv_addr, sizeof(serv_addr));
  serv_addr.sin_family = AF_INET;
  bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr,
        server->h_length);
  serv_addr.sin_port = htons(portno);
  if (connect(sockfd, (sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
    client_error("ERROR connecting");
  bzero(buffer, 256);
  sprintf(buffer, "%s", "Hello World!");
  n = write(sockfd, buffer, strlen(buffer));
  if (n < 0) client_error("ERROR writing to socket");
  bzero(buffer, 256);
  n = read(sockfd, buffer, 255);
  if (n < 0) client_error("ERROR reading from socket");
  printf("%s\n", buffer);
  close(sockfd);
  return 0;
}