CODEWITHSUNDEEP
udp
ejohnson
ejohnson

Reputation: 159

A bind socket request gives a EADDRNOTAVAIL

I have a small C program where I am trying to bind to a socket at a certain ip:port. Here it the program -

int main ()
{
    int udp_fd = -1;
    struct sockaddr_in sockaddr;

    char *ip = (char *)"xx.yyy.zzz.aaa";
    int port = 1234;
    udp_fd = socket(AF_INET, SOCK_DGRAM, 0);

    if (udp_fd == -1) {
       printf("Could not create socket\n");
       return -1;
    }

    sockaddr.sin_family = AF_INET;
    sockaddr.sin_addr.s_addr = inet_addr(ip);
    sockaddr.sin_port = htons(port);

    if (bind(udp_fd, (struct sockaddr *)&sockaddr, sizeof(sockaddr)) == -1) {
        printf("Could not bind to %s: %d: %d: %d\n", ip, port, errno, udp_fd);
        return -1;
    }

    if (fcntl(udp_fd, F_SETFL, O_NONBLOCK | O_ASYNC) < 0) {
        printf("Error setting socket as non-blocking \n");
        return -1;
    }

    return 0;
}

This fails with EADDRNOTAVAIL

define EADDRNOTAVAIL 99 /* Cannot assign requested address */

I try to connect to the same server from another device that is on the same network as the other device that fails the bind and it is successful.

There are no firewalls enabled on the failing device.

Upvotes: 0

Views: 3503

Answers (1)

user207421
user207421

Reputation: 311008

You are trying to bind your socket to a non-local IP address.

You don't generally need to bind to a specific IP address at all. Change:

sockaddr.sin_addr.s_addr = inet_addr(ip);

to

sockaddr.sin_addr.s_addr = INADDR_ANY;

Upvotes: 2

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