Close socket hangs in SunOS5.6

Question

The close() function is hanging when I attempt to close a socket. I have a small multi-threaded program, which I will attach below, which replicates the problem. Basically, the program creates a thread which listens for a datagram from a socket using the recvfrom() function. When the main thread attempts to close the socket being listened to, the close() function never returns. My guess is the recvfrom() function is doing some kind of blocking and somehow needs to be told to quit waiting. However, I'm not sure how one does this. Any ideas are greatly appreciated.
Sun tech. support recommended installing some patches we are missing. While that may ultimately be the solution, I would like to avoid doing so because this would affect multiple products we are developing and many of our customers.
The related portion of the code is:
main()
/* create thread using pthread_create() */
while (1) {
fgets(c, sizeof(c), stdin);
if (c[0] == '\n')
break;
fprintf(stderr, "Closing socket\n");
close(sockfd);
exit(0);
void wait_awhile(void) {
char buff[MAXLINE];
int n;
fprintf(stderr, "\nIN THREAD: prior to socket call\n");
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd < 0) {
fprintf(stderr, "could not create socket\n");
exit(0);
/* Get the server's socket address */
bzero((struct sockaddr_in *)&servaddr, sizeof(servaddr));
clientaddr_len = sizeof(struct sockaddr_in);
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(3500);
servaddr.sin_addr.s_addr = inet_addr(ip_address);
/* Bind it to the port */
fprintf(stderr, "IN THREAD: Binding socket\n");
if (bind(sockfd, (SA *) &servaddr, sizeof(servaddr)) < 0)
close(sockfd);
fprintf(stderr, "could not bind socket\n");
exit(0);
while (1)
fprintf(stderr, "IN THREAD: Waiting for datagram\n");
if ( (n = recvfrom(sockfd, buff, MAXLINE, 0, (SA *)&clientaddr, &clientaddr_len)) < 0)
close(sockfd);
}

Answer 1

"Shirley" <[email protected]> wrote:
>
"Khalid" <[email protected]> wrote:
We seem to have close wait problem in extreme load where apache/weblogic
hold the
tread so the socket cannot be closed. Does anyone know how to fix this
problem.
It seems like after in runs out of thread the server crashes.
Have you fixed this problem you were facing ,because we are facing exactly
the
same problem.Did you find any solution .If so please do let us know
Cheers
Shirley RemediosWe had the same problem and reduced the number of sockets in this state by reducing
the time to wait before closing the sockets. On Solaris we set 'tcp_time_wait_interval'
to 30000 (30 seconds) on the web and app servers.