Port Scanner in C (with Translation of Functions)

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#include //standard library function
#include //for socket n networking functions
#include //for socket function
#include //for networking
#include //for database......... not required........ here
#include //stad library function hope u guys know abt this
#include

/* Main programs starts*/
int main(int argc, char **argv) //argc
{
int sd; //socket descriptor
int port; //port number
int start; //start port
int end; //end port
int rval; //socket descriptor for connect
char response[1024]; //to receive data
char *message="shell"; //data to send
struct hostent *hostaddr; //To be used for IPaddress
struct sockaddr_in servaddr; //socket structure

if (argc < 4 ) { printf("------Created By www.Softhardware.co.uk-----------\n"); printf("--------------------------------------------------\n"); printf("Usage: ./tscan \n"); printf("--------------------------------------------------\n"); return (EINVAL); } start = atoi(argv[2]); //Takes the starting port number to scan from end = atoi(argv[3]); // FOr last port number that has to be scanned for (port=start; port<=end; port++) { //portno is ascii to int second argument sd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP); //created the tcp socket // PF_INET==family name AF_INET can also be used, SOCK_STREAM is how data bytes have to be sent, IPPRPTP_TCP== which protocol to follow, UDP or TCP if (sd == -1) // THis fucntion checks for the socket creation, if socket is created successful then continue else.... print error { perror("Socket()\n"); return (errno); } memset( &servaddr, 0, sizeof(servaddr)); servaddr.sin_family = AF_INET; //FAMILY NAME servaddr.sin_port = htons(port); //set the portno hostaddr = gethostbyname( argv[1] ); //get the ip 1st argument memcpy(&servaddr.sin_addr, hostaddr->h_addr, hostaddr->h_length);

//below connects to the specified ip in hostaddr

rval = connect(sd, (struct sockaddr *) &servaddr, sizeof(servaddr));
if (rval == -1)
{
printf("Port %d is closed\n", port);
close(sd);
}
else
printf("Port %d is open\n",port);

close(sd); //socket descriptor
}

}

[for unix platform]
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