/*  Author: David Foster      Date Created: June 14, 2000
 *  Last Modified: February 26, 2001
 *  DESCRIPTION: Simple TCP port scanner.  Provide the program 
 *	with a host and optional highest port number and it will 
 *	report which ports TCP connections can be made on.
 *  TO DO:  set l_linger and l_onoff with setsockopt so that
 *	we don't leave TIME WAIT states for all active connections
*/

#include <stdio.h>
#include <stdlib.h>  //for atoi
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>  // inet_pton, inet_ntop, inet_aton, inet_addr, inet_ntoa

#ifndef INET_ADDRSTRLEN
#define INET_ADDRSTRLEN 16
#endif

int main(int argc, char **argv){
    int sockfd, i, iport=1023, err;
    char *s, str_addr[INET_ADDRSTRLEN];
    struct sockaddr_in	servaddr;
    struct servent *sserv;
    struct hostent *shost;

	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	if(argc == 1){
	  printf("Usage: port <address or host> [highest port]\n"); 
	  exit(0);
	}

	// Convert the host argument to the proper format
	if(inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0){
	    printf("Attempting to resolve hostname %s....\n", argv[1]);
	    if((shost = gethostbyname(argv[1])) == NULL){
		perror("Could not resolve hostname");
		exit(0);
	    }else{
	    	memcpy(&servaddr.sin_addr, shost->h_addr, sizeof(struct in_addr));
	    }
	}
	inet_ntop(AF_INET, &servaddr.sin_addr, str_addr, INET_ADDRSTRLEN); 
	if(argv[2] ) iport = atoi(argv[2]);
	printf("Address: %s  Highest Port: %d\n", str_addr, iport);

//	servaddr.sin_port = htons(1);

////////////////////////////////////////
// Check all ports from 1 to high limit
////////////////////////////////////////
	for(i=1; i<=iport; i++){
  	   servaddr.sin_port = htons(i);
	   if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
		perror("error creating socket");
		exit(0);
	   }
	   sserv = getservbyport(htons(i), "tcp");

////////////////////////////////////////
// Try to connect to the current port
////////////////////////////////////////
	   if(connect(sockfd, (struct sockaddr*) &servaddr, sizeof(servaddr)) >= 0){
		write(sockfd, "quit", 4);
		shutdown(sockfd, 2);
//Does this port have a service name?  If so, let's find it and print it
		if(sserv == NULL){  	
		   printf("%4d [               ] - ACTIVE\n", i);
		}else{
		   printf("%4d [%-15s] - ACTIVE\n", i, sserv->s_name);
		}
	   }else{  //Connection refused
		if((err = errno) == 113){  // No route to host errno
	  	   perror("Connect error"); exit(0);
		}
		s = (char *) strerror(err);
// We don't need to print "connection refused" socket info
//		if(sserv == NULL){  
//		   printf("%4d [               ] - %s\n", i, s); 
//		}else{  
//		   printf("%4d [%-15s] - %s\n", i, sserv->s_name, s);
//		}
	   }
	   close(sockfd);
	}//end for loop		
	return(1);
}