showing bound sockets!!

Question

2.50/5 (2 votes)

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C

int sock ;  // Socket
int c ;    //  condition
struct sockaddr_in serveraddr ;  //AF_INET
unsigned short Portnumber = 3306 ; //Port#



sock = socket(AF_INET , SOCK_STREAM , 0) ;
if ( sock == -1 )
{
    error("socket()");
}

memset(&serveraddr , 0 , sizeof serveraddr);


serveraddr.sin_family = AF_INET ;
serveraddr.sin_port   = htons(Portnumber);
serveraddr.sin_addr.s_addr  = ntohl(INADDR_ANY);

bind(sock , (struct sockaddr *)&serveraddr , sizeof serveraddr);


system("netstat -pa --tcp 2>/dev/null ");

when i run this program i cant see my bound socket in output!!
please help,
i want to write a program that listen on a specific port and each client can connect to it.

Posted 21-Jul-12 21:45pm

Bathooman

Updated 21-Jul-12 22:06pm

Mehdi Gholam

v2

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Comments

Code-o-mat 22-Jul-12 5:43am

Not sure if this might help anything, but shouldn't you specify PF_INET for the third parameter of the socket call (where you have zero now)? Otherwise, this might be a synchronization-kind of problem, like, you do the bind call and then right after you do the netstat call, maybe the system didn't have time yet to completely register your socket as bound? Or maybe your socket will be only listed if you also call 'accept'?

[no name] 22-Jul-12 5:47am

Let's check it sir!!!!

Code-o-mat 22-Jul-12 5:55am

Huh?

pasztorpisti 23-Jul-12 18:53pm

If I remember right AF_INET and PF_INET are exchangeable. The third parameter is usually IPPROTO_TCP but I have seen zero there in a lot of examples (especially on linux).

bbirajdar 22-Jul-12 15:18pm

What ????????????????

Sergey Alexandrovich Kryukov 22-Jul-12 18:32pm

What do you mean by "see a socket"? If you need to implement communication through sockets, implement it. What's the question, exactly?
--SA

pasztorpisti 23-Jul-12 18:45pm

Well, the question isn't written down but reading the post reminds me a very common probelm I encountered when I developed tcp socket applications. If you start a server for debugging, and you just kill the application then you can not restart your server for some time (about 1-2minutes) because the listen port is bound (bind returns with error) despite the fact that your server program is already dead and isn't running. This happens because the operating system keeps your socket object alive even after you closed it because it isn't sure that every opeartion on the socket has already completed (read/write/handshake/shutdown sequence). This feature is called LINGER. its usually turned on by default. To avoid this behavior in the operating system you should make sure that this feature is turned on and the linger timeout is set to zero. Check out setsockopt() and SO_LINGER (and the windows specific SO_DONTLINGER) if your problem is what I described above.
EDIT: sorry, I totally misunderstood the question. :D I think it depends on the network stack implementation when the socket actually gets registered into specific tables. I'm not sure if your bound socket pops up in the netstat list before you call listen() on it - that is, you put it into work.

James R. Twine 25-Jul-12 13:43pm

I thought you would only see active sockets in NETSTAT, so you would have to either called a listen on it, or have it connected to something.

pasztorpisti 25-Jul-12 19:06pm

Your assumption is probably true, I'm just unsure about the implementation of bind() function on different platforms. The bind() function can return WSAEADDRINUSE this is the reason for me to suspect that bind() already puts the socket somewhere so it can find out if bound addresses are unique.

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