listen(): invalid argument - c

Question

Trying to create a server-client application, and I'm having quite a bit of trouble setting up the connection on the server-side. After setting up the socket, and bind()ing the socket, my listen()-call fails with the error message
listen: Invalid argument
which I get from perror()-ing the case where listen() returns -1.
The synopsis of the program is the following: I use getaddrinfo() to generate a linked list of struct addrinfo's, loop through that until I find one that I can successfully create a socket with, then bind() and finally listen().
The listen() call goes as follows:
if ((status = listen(socket_fd, BACKLOG_SIZE)) == -1) {
perror("listen");
close(socket_fd);
freeaddrinfo(res);
exit(EXIT_FAILURE);
}
To be sure, I've printed the values of socket_fd and BACKLOG_SIZE, turning out to be 3 and 5, respectively. Have been debugging for hours now, and I simply cannot find out where the problem lies. Haven't found anyone with the same issue on stackOverflow, either...
Thank you in advance for any help!
Full program:
int main(int argc, char* argv[]) {
int port_no = server_usage(argc, argv);
ready_connection(port_no);
/* Synopsis:
getaddrinfo()
socket()
bind()
listen()
accept()
*/
int socket_fd = setup_socket(NULL, port_no);
struct sockaddr_storage their_addr;
socklen_t addr_size = sizeof(their_addr);
int new_fd = 0;
// Allow reuse of sockets
int activate=1;
setsockopt(socket_fd, IPPROTO_TCP, TCP_NODELAY, &activate, sizeof(int));
if ((status = bind(socket_fd, res->ai_addr, res->ai_addrlen)) == -1) {
perror("bind");
exit(EXIT_FAILURE);
}
if ((status = connect(socket_fd, res->ai_addr, res->ai_addrlen)) == -1) {
perror("connect");
close(socket_fd);
freeaddrinfo(res); // free the linked-list
exit(EXIT_FAILURE);
}
if ((status = listen(socket_fd, BACKLOG_SIZE)) == -1) {
perror("listen");
close(socket_fd);
freeaddrinfo(res); // free the linked-list
exit(EXIT_FAILURE);
}
if ((new_fd == accept(socket_fd, (struct sockaddr *)&their_addr, &addr_size)) == -1) {
perror("accept");
exit(EXIT_FAILURE);
}
char buffer[BUFSIZE];
recv(new_fd, buffer, BUFSIZE, 0);
close(socket_fd);
close(new_fd);
freeaddrinfo(res); // free the linked-list
return 0;
}
setup_socket()-function:
int setup_socket(char* hostname, int port_no) {
// hints is mask struct, p is loop variable
struct addrinfo hints, *p;
memset(&hints, 0, sizeof hints); // make sure the struct is empty
// TODO IPv6-support?
hints.ai_family = AF_INET; // only IPv4 supported
hints.ai_socktype = SOCK_STREAM; // TCP stream sockets
hints.ai_flags = AI_PASSIVE; // fill in my IP for me
char port_str[6]; // max port size is 5 digits + 0-byte
memset(port_str, 0, 6);
sprintf(port_str, "%d", port_no);
if ((status = getaddrinfo(hostname, port_str, &hints, &res)) == -1) {
fprintf(stderr, "getaddrinfo error: %s\n", gai_strerror(status));
exit(EXIT_FAILURE);
}
int socket_fd = 0;
for (p = res; p != NULL; p = p->ai_next) {
if ((socket_fd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
perror("socket");
exit(EXIT_FAILURE);
}
}
if (socket_fd == 0) {
errno = ENOTSOCK;
perror("no socket");
exit(EXIT_FAILURE);
}
return socket_fd;
}

Answer 1

You cannot connect(), then listen() on the same socket. Lose the connect().