reverse_telnet.c

ICS 课程的Lab8

/*  Blake Scholl
 *  [e-mail]
 *
 *  a "reverse telnet" implementation for
 *  investigating the behavior of HTTP clients
 *
 *
 */

/********** Includes *********/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <unistd.h>
#include <fcntl.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <signal.h>

int main(int argc, char *argv[])
{
  int listenFD;
  int connFD;
  int on = 1;

  fd_set readFDs;

  int retval;
  struct sockaddr_in local; /* local socket addr */
  short portnum;

  struct sockaddr_in remote_addr;
  int len;


  if(argc != 2)
    {
      printf("Usage: %s <port number>\n", argv[0]);
      exit(0);
    }

  portnum = atoi(argv[1]);
  printf("Attempting to listen on port %d.\n", portnum);

/* open up a TCP socket */
  listenFD = socket(AF_INET, SOCK_STREAM, 0);

  /* try and reuse address */
  if (setsockopt(listenFD, SOL_SOCKET, SO_REUSEADDR, &on, sizeof (on)) < 0)
    {

      fprintf(stderr, "Findsplitter: Error setting SO_REUSEADDR.\n");
    }

  local.sin_family = AF_INET;
  local.sin_port = htons(portnum);
  local.sin_addr.s_addr = INADDR_ANY;
  bzero(&(local.sin_zero),8);


  retval = bind(listenFD, (struct sockaddr *) &local, sizeof(struct sockaddr));
  if(retval == -1)
    {
      fprintf(stderr, "Error binding socket.\n");
      exit(1);
    }


  /* Listen for inbound connections */

  if(listen(listenFD, 10) == -1)
    {
      fprintf(stderr, "Unable to listen.\n");
      exit(1);
    }

  connFD = accept(listenFD, (struct sockaddr *)  &remote_addr, &len);


  printf("%s: Got a connection: FD #%d\n", argv[0], connFD);



  while(1)
    {
      FD_ZERO(&readFDs);
      FD_SET(connFD, &readFDs);
      FD_SET(0, &readFDs);


      if( select(connFD+1, &readFDs, NULL, NULL, NULL))
	{

	  if(FD_ISSET(connFD, &readFDs))
	    {
	      char buf[4096];

	      int bytes;

	      bytes = recv(connFD, (void *) buf, 4096, 0);
	      if(bytes != ECONNRESET && bytes!=0)
		{
		  buf[bytes] =0;
		  printf("%s", buf);
		}

	    }

	  if(FD_ISSET(0, &readFDs))
	    {
	      char buf[4096];

	      int bytes;

	      bytes = read(0, (void *) buf, 4096);
	      if(bytes != ECONNRESET && bytes!=0)
		{
		  buf[bytes] =0;
		  write(connFD,  buf, strlen(buf) +1);
		}

	    }
	}
    }
}