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IP number (for example Ox7FOOOOO I is 127.0.0. 1). So how do we convert the result in host->h3ddr
given by gethostbyname(3)? Easy, we'll just cast the host->h_addr with *(long *)(host->h_addr). Fi­
nally, don't fo rget to use the htons(3) to convert it to revers byte order on x86. And the addrlen argu­
ment is just sizeof(sockaddr). We will have to cast our sockaddr_in variable to a sockaddr struct when
passing it to connect(2). And of course, one final thing, don't forget to close down your socket. Use
close(2) with your socket as argument. Like: close(s) (The definition of close(2) is found in
.)
Writing The Code
Now when your fingertips are itching to get down to business don't let me hold you back. Yo u
should without problem be able to write a portscanner or anything else - only your imagination sets the
limit. No guide is complete without that final piece of source code, so here it is:
portscan. c
#include
#include
#include
#include
#include
#include
#include
#defi ne START
#define STOP 1024
void main(int argc, char " argv) {
tnt 5,port;
struct hostent 'host;
struct sockaddr_in victim;
printf("PortScan v1.0 - By darknite[@kurir.net]\n");
printfC"For his socket-programming article in 1998\n");
if (argc