Dear all,

I have a problem with binding a server socket on a mac os x 10.5.8.
The problem is that every time i try to bind the socket to the address it gives the following error "Address already in use". I know that it means there is another process using that port, but there isn't any. I tried restarting the computer, using a different mac, a sample online code from a tutorial, using different ports but no use.
I checked the ports using netstat, and it's not used. When I run the program, the netstat will give a result that my program is listening on that port but on the other hand, the program exits with the specified error.

Is there anything that i am missing?
I am using xcode, and the C code is used in an objecive-c program.

I appreciate any help,
Best regards,

Which port(s) are you trying to bind to?

And can we see the code..

Edited 6 Years Ago by gerard4143: n/a

At the following example, i am using port 8998

This sample code is taken from "Beej's Guide to network programming"

/*
 ** server.c -- a stream socket server demo
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>

#define PORT "8998"  // the port users will be connecting to

#define BACKLOG 10     // how many pending connections queue will hold

void sigchld_handler(int s)
{
    while(waitpid(-1, NULL, WNOHANG) > 0);
}

// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }
	
    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(void)
{
    int sockfd, new_fd;  // listen on sock_fd, new connection on new_fd
    struct addrinfo hints, *servinfo, *p;
    struct sockaddr_storage their_addr; // connector's address information
    socklen_t sin_size;
    struct sigaction sa;
    int yes=1;
    char s[INET6_ADDRSTRLEN];
    int rv;
	
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE; // use my IP
	
    if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }
	
    // loop through all the results and bind to the first we can
    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype,
							 p->ai_protocol)) == -1) {
            perror("server: socket");
            continue;
        }
		
        if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
					   sizeof(int)) == -1) {
            perror("setsockopt");
            exit(1);
        }
		
        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            perror("server: bind");
            continue;
        }
		
        break;
    }
	
    if (p == NULL)  {
        fprintf(stderr, "server: failed to bind\n");
        return 2;
    }
	
    freeaddrinfo(servinfo); // all done with this structure
	
    if (listen(sockfd, BACKLOG) == -1) {
        perror("listen");
        exit(1);
    }
	
    sa.sa_handler = sigchld_handler; // reap all dead processes
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_RESTART;
    if (sigaction(SIGCHLD, &sa, NULL) == -1) {
        perror("sigaction");
        exit(1);
    }
	
    printf("server: waiting for connections...\n");
	
    while(1) {  // main accept() loop
        sin_size = sizeof their_addr;
        new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
        if (new_fd == -1) {
            perror("accept");
            continue;
        }
		
        inet_ntop(their_addr.ss_family,
				  get_in_addr((struct sockaddr *)&their_addr),
				  s, sizeof s);
        printf("server: got connection from %s\n", s);
		
        if (!fork()) { // this is the child process
            close(sockfd); // child doesn't need the listener
            if (send(new_fd, "Hello, world!", 13, 0) == -1)
                perror("send");
            close(new_fd);
            exit(0);
        }
        close(new_fd);  // parent doesn't need this
    }
	
    return 0;
}

The output is
server: bind: Address already in use
server: waiting for connections...

Could you print out your netstat output after you run the server

netstat -a | grep tcp

Edited 6 Years Ago by gerard4143: n/a

Thanks for your reply,

Before running the server:
tcp4 0 0 10.0.0.15.49160 bzq-84-109-42-23.13505 ESTABLISHED
tcp4 0 0 *.21039 *.* LISTEN
tcp4 0 0 localhost.64000 *.* LISTEN
tcp4 0 0 *.mysql *.* LISTEN
tcp4 0 0 localhost.ipp *.* LISTEN
tcp6 0 0 localhost.ipp *.* LISTEN
tcp4 0 0 10.0.0.15.49172 12.120.11.223.http TIME_WAIT
tcp4 0 0 10.0.0.15.49173 bjango.com.http TIME_WAIT


After running it:
tcp4 0 0 *.8998 *.* LISTEN
tcp46 0 0 *.8998 *.* LISTEN
tcp4 0 0 10.0.0.15.49160 bzq-84-109-42-23.13505 ESTABLISHED
tcp4 0 0 *.21039 *.* LISTEN
tcp4 0 0 localhost.64000 *.* LISTEN
tcp4 0 0 *.mysql *.* LISTEN
tcp4 0 0 localhost.ipp *.* LISTEN
tcp6 0 0 localhost.ipp *.* LISTEN
tcp4 0 0 10.0.0.15.49254 74.125.6.152.http TIME_WAIT
tcp4 0 0 10.0.0.15.49253 wy-in-f139.1e100.http TIME_WAIT

Could you print out your netstat output after you run the server

netstat -a | grep tcp

Try this slimmed down server. Will it work/compile on your system if so did it set up a server on port 50000?

#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <string.h>
#include <signal.h>

#define DEFAULT_PROTOCOL 0

int main(int argc, char**argv)
{
	int listenfd, connfd;
	struct sockaddr_in servaddr;

	listenfd = socket(AF_INET, SOCK_STREAM, DEFAULT_PROTOCOL);

	memset(&servaddr, 0, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(50000);
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);

	bind(listenfd, (const struct sockaddr*)&servaddr, sizeof(servaddr));

	listen(listenfd, 5);

	for(;;)
	{
		connfd = accept(listenfd, NULL, NULL);

		/*do something server like*/
	}
	exit(EXIT_SUCCESS);
}

I tried it and added an error checking on binding function. Same result. But finally it managed to communicate with the server from the client socket despite the binding error.
Maybe I should just ignore this error and see how it goes
Thanks a lot for your help. I really appreciate it

I tried compiling your code over here and it generated a whole pile of errors and warnings when I used these switches

gcc filemane.c -Wall -ansi -pedantic -o filename

It compiled fine when I used

gcc filemane.c -o filename

This statement alone isn't very good...But it did compile and is running without incident.

The output:

server: waiting for connections...
[1] 16980

netstat -a | grep tcp

tcp        0      0 *:mysql-im                  *:*                         LISTEN      
tcp        0      0 *:8998                      *:*                         LISTEN

Edited 6 Years Ago by gerard4143: n/a

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