asked on

unable to create listening socket

SunOS:

I have a daemon program which opens a listening socket and accept requests. The program is work fine. Problem is that after the program terminates (the listening socket is closed and close() returns 0), if you run the daemon again, sometimes it will fail to create the socket (bind to the port), after several minutes it will be OK.

Any idea?

rdelfino

Try using setsockopt() and setting SO_REUSEADDR

If bind fails after setting this option, the port is
in use by another process.

Example:

#define PORT 3333

struct sockaddr_in sAddr;
int s, opt;

s = socket(AF_INET, SOCK_STREAM, 0);
opt = 1;
setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char*)&opt, sizeof(int));
memset(&sAddr, 0,sizeof(sAddr));

sAddr.sin_family = AF_INET;
sAddr.sin_port = htons(PORT);
sAddr.sin_addr.s_addr = inet_addr("111.111.111.111");

if (bind(s, (struct sockaddr*)&sAddr, sizeof(sAddr)) < 0)
{
// the port is in use by another process
}

I hope it helps

Reginaldo

faster

ASKER

NO it does not work. The port seems to be used by the died process until several minutes later.

faster

ASKER

Sorry, my mistake. It works. Please re-submit your answer.

Could you please explain what causes this problem and why this setting can work?

helver

Unless you use the REUSEADDR socket option, the port will be in use until it times out. I think (may be wrong on this - didn't do any checking) that the socket has to remain open for a period of time as specified by the TCP protocol to allow and client connection to acknowlege closing the connection.

What you must be careful of, however, is accidently binding again to the same socket. This could cause a bad situation where multiple processes compete to read data from the socket. This is generally a bad thing.

faster

ASKER

under normal situation, there should not be such timeout. There must be something speical and that what I am interested.

jonalee

I have also encounter this problem.
I slove it by calling shutdown(2) first, then call close();
I have tryied it in my application, it works without problem.

ASKER CERTIFIED SOLUTION

kannan042597

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faster

ASKER

Sorry Kannan, since rdelfino answered the question first, the points should go to him. If in the next several days he does not show up, I will accept your answer.

rdelfino

Oops;

I've made a mistake in the code I've sent.

Instead of:
sAddr.sin_addr.s_addr = inet_addr("111.111.111.111");

Try:
sAddr.sin_addr.s_addr = INADDR_ANY;

Reginaldo