/* NVT.c -- simple telnet for WIN32-console
 *
 * Author
 *   Hirofumi Fujii (Hirofumi.FUJII@kek.jp)
 *
 * Status
 *   Public Domain
 * 
 * History
 *   07-Jun-1996  1st draft version
 *
 * Compile/Link
 * MS VC++ 4.0J
 *    cl /MT nvt.c wsock32.lib
 *
 * References
 *   RFC 854 (Telnet Protocol Specification)
 *   RFC 855 (Telnet Option Specifications)
 *   RFC 856 (Telnet Binary Transmission)
 *   RFC 857 (Telnet Echo Option)
 *   RFC 858 (Telnet Suppress Go Ahead Option)
 *   RFC 859 (Telnet Status Option)
 *   RFC 860 (Telnet Timing Mark Option)
 *   RFC 861 (Telnet Extended Options - List Option)
 *
 */

#define STRICT
#include <windows.h>
#include <winsock.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <conio.h>
#include <process.h>

/* Definitions */
#define TELNET_SE      240
#define TELNET_NOP     241
#define TELNET_DM      242
#define TELNET_BRK     243
#define TELNET_IP      244
#define TELNET_AO      245
#define TELNET_AYT     246
#define TELNET_EC      247
#define TELNET_EL      248
#define TELNET_GA      249
#define TELNET_SB      250
#define TELNET_WILL    251
#define TELNET_WONT    252
#define TELNET_DO      253
#define TELNET_DONT    254
#define TELNET_IAC     255

#define TELOPT_ECHO      1
#define TELOPT_SUPP      3
#define TELOPT_STATUS    5
#define TELOPT_TM        6
#define TELOPT_EXOPL   255

/* Prototypes */
void main( int argc, char *argv[] );         /* Thread 1 */
void RecvProc( void* );                      /* Thread 2 */

/* Global Variables */
HANDLE hScreenMutex;
HANDLE hSendSockMutex;
int RunFlag;
HANDLE hRunMutex;
SOCKET sockfd;

/* Body */

int
netstart( void )
{
  WSADATA wsadata;
  WORD wsaversion;

  wsaversion = 0x0101;
  return( WSAStartup( wsaversion, &wsadata ) );
}

void
netclose( SOCKET sockfd )
{
  closesocket( sockfd );
  WSACleanup();
  return;
}

void
main( int argc, char *argv[] )
{
  unsigned long inaddr;
  struct hostent *hp;
  struct sockaddr_in serv_addr;
  short remoteport;
  int cont;
  int n;
  int Keycode;
  char ch;

  /* Check the number of arguments */
  if( (argc != 2) && (argc != 3) )
  {
    fprintf( stderr, "Usage: %s hostname [port]\n", argv[0] );
    return;
  }

  /* Start network module */
  if( netstart() != 0 )
  {
    fprintf( stderr, "Cannot start the network.\n" );
    return;
  }

  /* Clear the server address */
  memset( (char *)&serv_addr, 0, sizeof( serv_addr ) );

  /* Get the server address */
  if( (inaddr = inet_addr( argv[1] )) != INADDR_NONE )
  {
    /* OK, It's dotted-decimal format */
    memcpy( (char *)&serv_addr.sin_addr, (char *)&inaddr, sizeof( inaddr ) );
  }
  else
  {
    /* Try to get hostaddress by using gethostbyname */
    if( (hp = gethostbyname( argv[1] )) == NULL )
    {
      WSACleanup();
      fprintf( stderr, "Error to get the hostaddress of %s\n", argv[1] );
      return;
    }
    memcpy( (char *)&serv_addr.sin_addr, hp->h_addr, hp->h_length );
  }

  if( argc == 2 )
    remoteport = IPPORT_TELNET;
  else
    remoteport = atoi( argv[2] );

  serv_addr.sin_port = htons( remoteport );
  serv_addr.sin_family = AF_INET;
  
  /* Create TCP socket */
  if( (sockfd = socket( AF_INET, SOCK_STREAM, 0 )) == INVALID_SOCKET )
  {
    WSACleanup();
    fprintf( stderr, "Cannot create TCP socket\n" );
    return;
  }
  
  fprintf( stderr, "Trying %s...\n", inet_ntoa( serv_addr.sin_addr ) );
  /* Connet to the server */
  if( connect( sockfd, (struct sockaddr *)&serv_addr, sizeof( serv_addr ) )
        < 0 )
  {
    netclose( sockfd );
    fprintf( stderr, "Cannot connect to the server\n" );
    return;
  }

  fprintf( stderr, "Connected to %s.\n", argv[1] );
  fprintf( stderr, "Escape character is '^]'.\n" );

  /* Create Mutex */
  hScreenMutex = CreateMutex( NULL, TRUE, NULL );
  hSendSockMutex = CreateMutex( NULL, TRUE, NULL );
  hRunMutex = CreateMutex( NULL, TRUE, NULL );

  cont = RunFlag = -1;
  ReleaseMutex( hScreenMutex );
  ReleaseMutex( hSendSockMutex );
  ReleaseMutex( hRunMutex );
  _beginthread( RecvProc, 0, NULL );

  while( cont )
  {
    Keycode = _getch();
    if( Keycode == 0x1d )
    {
      WaitForSingleObject( hRunMutex, INFINITE );
      RunFlag = 0;
      ReleaseMutex( hRunMutex );
    }
    else
    {
      ch = Keycode;
      WaitForSingleObject( hRunMutex, INFINITE );
      cont = RunFlag;
      ReleaseMutex( hRunMutex );
      if( cont )
      {
        WaitForSingleObject( hSendSockMutex, INFINITE );
        n = send( sockfd, &ch, 1, 0 );
        ReleaseMutex( hSendSockMutex );
        if( n != 1 )
        {
          WaitForSingleObject( hScreenMutex, INFINITE );
          fprintf( stderr, "Send Error\n" );
          ReleaseMutex( hScreenMutex );
          WaitForSingleObject( hRunMutex, INFINITE );
          cont = RunFlag = 0;
        }
      }
    }
    WaitForSingleObject( hRunMutex, INFINITE );
    cont = RunFlag;
    ReleaseMutex( hRunMutex );
  }

  /* All Done */
  CloseHandle( hRunMutex );
  CloseHandle( hSendSockMutex );
  CloseHandle( hScreenMutex );

}

void
SendTelOpt( unsigned int cmd, unsigned int opt )
{
  unsigned char ch[3];

  ch[0] = TELNET_IAC;
  ch[1] = cmd;
  ch[2] = opt;

  WaitForSingleObject( hSendSockMutex, INFINITE );
  send( sockfd, ch, 3, 0 );
  ReleaseMutex( hSendSockMutex );
}

void
RecvProc( void* p )
{
  unsigned char ch;
  unsigned int c;
  unsigned int uIACcmd;
  unsigned int uIACopt;
  int n;
  int inIAC;

  inIAC = 0;
  while( (n = recv( sockfd, &ch, 1, 0 )) == 1 )
  {
    if( ch == 0xff )
    {
      if( inIAC )
      {
        WaitForSingleObject( hScreenMutex, INFINITE );
        c = ch;
        fputc( c, stdout );
        inIAC = 0;
      }
      else
      {
        inIAC = 1;
      }
    }
    else
    {
      if( inIAC )
      {
        if( inIAC == 1 )
        {
          uIACcmd = ch; inIAC++;
        }
        else
        {
          uIACopt = ch;
          if( uIACcmd == TELNET_WILL )
          {
            if( (uIACopt == TELOPT_ECHO) || (uIACopt == TELOPT_SUPP) )
            {
              SendTelOpt( TELNET_DO, uIACopt );
            }
            else
            {
              SendTelOpt( TELNET_DONT, uIACopt );
            }
          }
          else if( uIACcmd == TELNET_DO )
          {
            SendTelOpt( TELNET_WONT, uIACopt );
          }
          inIAC = 0;
        }
      }
      else
      {
        WaitForSingleObject( hScreenMutex, INFINITE );
        c = ch;
        if( c != 0 ) fputc( c, stdout );
        ReleaseMutex( hScreenMutex );
      }
    }
  }
  WaitForSingleObject( hRunMutex, INFINITE );
  RunFlag = 0;
  ReleaseMutex( hRunMutex );
  WaitForSingleObject( hScreenMutex, INFINITE );
  fprintf( stderr, "Connection closed\n" );
  ReleaseMutex( hScreenMutex );
}