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help me in accessing LAN using C programming

Posted on 2004-03-28
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Last Modified: 2010-04-15
Hi all!
i'm trying to access LAN using C programming.
till now i could access serial port, but i'm not sure how to acess LAN.
could someone help me in this regard!!!!

thanks in advance.

vasu
0
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Question by:vasureddym
6 Comments
 

Expert Comment

by:PCT
ID: 10701918
If you what to send data through your Ethernet card you can use Sockets.
You will have to include some header probably socket.h for unix or winsock.h for windows into your code.

Don't forget to include the required libraries before compiling.


0
 
LVL 12

Expert Comment

by:stefan73
ID: 10702264
Hi vasureddym,
Depends on what you mean by "access LAN". Low-level access of network card?
Or do you want to access a particular server via SMB?
Do you want to access some TCP/IP service, like FTP?

Cheers,
Stefan
0
 
LVL 45

Expert Comment

by:sunnycoder
ID: 10710771
ok heres what you need to do

open a socket:


fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL));
if (fd < 0) {
sprintf(ebuf, "socket: %s", strerror(errno));
goto failed;
}



/* check device type */

memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
if (ioctl(fd, SIOCGIFHWADDR, &ifr) < 0 ) {
sprintf(ebuf, "SIOCGIFHWADDR: %s", strerror(errno));
goto failed;
}

if (ifr.ifr_hwaddr.sa_family != ARPHRD_ETHER) {
sprintf(ebuf, "unsupported physical layer type 0x%x (ethernet
only)",
ifr.ifr_hwaddr.sa_family);
goto failed;
}


memcpy(ethaddr, ifr.ifr_hwaddr.sa_data, ETH_ALEN);


if you need promisc mode, don't forget to restore device flags.


ifr.ifr_flags |= IFF_PROMISC;
if (ioctl(fd, SIOCSIFFLAGS, &ifr) < 0 ) {
sprintf(ebuf, "SIOCSIFFLAGS: %s", strerror(errno));
goto failed;
}
atexit(restore_ifr);


/****/


void restore_ifr(void)
{
int fd;


fd = socket(PF_INET, SOCK_PACKET, htons(0x0003));
if (fd < 0)
fprintf(stderr, "linux socket: %s", strerror(errno));
else if (ioctl(fd, SIOCSIFFLAGS, &saved_ifr) < 0)
fprintf(stderr, "linux SIOCSIFFLAGS: %s", strerror(errno));
}


To receive/send stuff, use recvmsg/sendmsg,
look into the concepts of the structs:
msghdr, ethhdr, iovec, and sockaddr_pkt to build/decode packages.

for more info http:20660168.html
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LVL 2

Author Comment

by:vasureddym
ID: 10721449
Hi all!

Thanks PCT for your Participation.

Hi Stefan73, all I want is to learn accessing/transferring files on LAN using protocols like TCP/IP.
I tried the following simple program. It, is not making use of any protocols.
thanks for your participation.

Hi sunnycoder, i'm beginner to Network programming in C. terms like 'sockets' are new to me,. can you suggest me something..
0
 
LVL 45

Accepted Solution

by:
sunnycoder earned 50 total points
ID: 10721477
www.ecst.csuchico.edu/~beej/guide/net/html/

go though it .. by the time you finish it, you would no longer feel like a beginner ;o)
0
 
LVL 2

Author Comment

by:vasureddym
ID: 10958535
thanks sunny!
i found that link very useful!
i didn't go through it completely. right now i'm  in another project, so i have to keep this topic aside for few days.
however, it is not a good idea to keep this Question for so long time.
i want to close this for the time being.
anyways, thanks
-vasureddym
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