#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netinet/in.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <time.h>
#include <arpa/inet.h>

int main(int argc, char * argv[])
{ if (argc != 2)
  { fprintf(stderr, "usage: %s portnumber\n", argv[0]);
    exit(1); }
  int port_number = atoi(argv[1]);

  int namemax = sysconf(_SC_HOST_NAME_MAX);
  char * ourname = malloc(namemax + 1);
  gethostname(ourname, namemax);
  printf("%s, port %d\n", ourname, port_number);
  int serversocket = socket(AF_INET, SOCK_STREAM, 0);

  struct sockaddr_in server_address;
  server_address.sin_len = sizeof(server_address);
  server_address.sin_family = AF_INET;
  server_address.sin_port = htons(port_number);
  server_address.sin_addr.s_addr = htonl(INADDR_ANY);

  int r = bind(serversocket, (struct sockaddr *) & server_address, sizeof(server_address));
  if (r < 0)
  { perror("bind");
    exit(1); } 

  r = listen(serversocket, 3);
  if (r < 0)
  { perror("listen");
    exit(1); } 

  while (1)
  { struct sockaddr_in client_address;
    socklen_t slen;
    int clientsocket = accept(serversocket, (struct sockaddr *) & client_address, & slen);
    if (clientsocket < 0)
    { if (clientsocket == EINTR)
        continue;
      perror("accept");
      exit(1); }

    printf("Accepted connection from %s port %d\n", inet_ntoa(client_address.sin_addr),
                                                    ntohs(client_address.sin_port));

    FILE * in = fdopen(clientsocket, "r");
    FILE * out = fdopen(clientsocket, "w");

    while (1)
    { char line[1000];
      char * s = fgets(line, 1000, in);
      if (s == NULL)
        break;
      printf("%s", line); }

    fclose(out);
    fclose(in);
    close(clientsocket); } }