setsockopt() doesn't unbind - c

Question

The following server in C doesn't work as expected. Upon running it the first time, no issues occur. Every next time you run it, it fails to bind. The solution of the question that some of you will probably mark as duplicate doesn't work either, regardless of the fact that setsockopt(...) is successful.
#include <stdio.h>
#include <netinet/in.h>
#include <string.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#define PORT 8080
#define SA struct sockaddr
int main() {
int sockfd, connfd;
struct sockaddr_in servaddr, cli;
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if(sockfd == -1) puts("Socket creation failed."), exit(0);
else puts("Socket created.");
const int optVal = 1;
const socklen_t optLen = sizeof(optVal);
setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &optVal, optLen);
servaddr.sin_family = AF_INET, servaddr.sin_port = htons(PORT);
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(sockfd, (SA *) &servaddr, sizeof(servaddr))) {
puts("Bind failed.");
shutdown(sockfd, 2);
return 12;
}
else puts("Bound.");
if(listen(sockfd, 5)) puts("Listen failed."), exit(2);
else puts("Listening: ");
int len = sizeof(cli);
connfd = accept(sockfd, (SA*)&cli, &len);
if(connfd < 0) puts("Connection failed."), exit(3);
else puts("Accepted.");
close(connfd);
return 0;
}
Things I've tried so far:
using setsockopt(...) has no effect
shutdown(...) doesn't work either
closesocket(...) is part of the Windows API, which I just have no intention to use
If I decide to ignore the "Address already in use" error, accept(...) fails with Invalid argument
If it matters I'm using CLion with cygwin under Windows 10.

Answer 1

"If it matters I'm using CLion with cygwin under Windows 10."
I strongly suspect that this matters.
When I compile your code exactly as you posted it, it behaves according to your desired / expected behavior.
When I comment out the setsockopt() call, I need to wait until the TIME_WAIT expires before being able to re-bind the same address+port, which is also expected.
I'm using gcc on macOS, so I suspect that your compilation and/or runtime environment has something to do with your code not working as expected for you. One way you could verify this if you don't have access to a physical Linux machine, and if you cannot set up dual-boot on the Windows machine that you do have, would be to spin up a small Linux instance at Digital Ocean, AWS, or some other cloud provider.
EDIT #1
I repeated this on a DO Linux host, and I have confirmed that your original code works as expected.