Thread: BSD Sockets: Finding a clients IP

Well, as outlined in another thread I have coded something similar to a SSH server.

Now I would like to be able to print the clients IP address to log files. How would I retreive the IP?

I would think its located in the struct passed to accept(). But where?

Thanks!
Moddy

Yes. Moved.

Here's an extract from Beej's Guide To Network Programming you may find useful.

4.11. DNS–You say "whitehouse.gov", I say "198.137.240.92"

In case you don’t know what DNS is, it stands for "Domain Name Service". In a nutshell, you tell it what the human-readable address is for a site, and it’ll give you the IP address (so you can use it with bind(), connect(), sendto(), or whatever you need it for.) This way, when someone enters:

$ telnet whitehouse.gov

telnet can find out that it needs to connect() to "198.137.240.92". But how does it work? You’ll be using the function gethostbyname():

Code:

#include <netdb.h>
struct hostent *gethostbyname(const char *name);

As you see, it returns a pointer to a struct hostent, the layout of which is as follows:

Code:

struct hostent {
char *h_name;
char **h_aliases;
int h_addrtype;
int h_length;
char **h_addr_list;
};
#define h_addr h_addr_list[0]

And here are the descriptions of the fields in the struct hostent:
• h_name – Official name of the host.
• h_aliases – A NULL-terminated array of alternate names for the host.
• h_addrtype – The type of address being returned; usually AF_INET.
• h_length – The length of the address in bytes.
• h_addr_list – A zero-terminated array of network addresses for the host. Host addresses are in Network Byte
Order.
• h_addr – The first address in h_addr_list.[/quote]