C, Bind faild: `Address Already in Use` - c

Question

I am writing a client-server program in C. I am getting an error in Bind function says: Address Already in Use. So I tired to use memset() and I got error says: Invalid Argument. Finally, I looked for similar questions on here, and some of them suggesting the use of setsocketopt() function. I used it and I am getting error says:
/tmp/ccBNsJtU.o: In function main:
socket.c:(.text+0xd0): undefined reference to setsocket
collect2: error: ld returned 1 exit status
I looked at almost-if-not all the similar questions even in different programing languages. Now I am stuck. Do I have to use setsocket() and if I do, is it causing a problem in my code? Or I don't have to use it and the problem is somewhere else? Could the problem be in the client or the server functions where I listen and send messages? This is the part of the code where the bind() and setsocket() functions are:
int main (void) {
int sl, sa, bn, erro, lis;
int status;
//server log socket
struct sockaddr_un server = {AF_UNIX, "log_server"};
sl = socket (AF_UNIX, SOCK_STREAM, 0);
if(sl < 0) {
perror("Faild to create socket - in main");
exit(1);
}
//I added this part
if (setsocket(sl, SOL_SOCKET, SO_REUSEADDR, &server, sizeof(server)) == -1) {
perror("setsocket - in main");
exit(1);
}
bn = bind (sl, (struct sockaddr *)&server, sizeof(server));
if(bn < 0){
perror("Faild to bind - in main");
exit(1);
}
lis = listen (sl, 1); //to be changed to 4
if (lis < 0) {
perror("Faild to listen - in main");
}

Answer 1

"Address already in use" typically means that some other socket is already bound to the given port. This could mean that there's a running program actively listening on that port, or it could mean that a prior instance of your program which is no longer running still has some socket resources open in the OS.
In the latter case, a call to setsockopt (not setsocket) with the SO_REUSEADDR parameter will address this. The fourth parameter should be a pointer to a char whose value is 1, while the fifth parameter should be sizeof(char).

Answer 2

For the users who are facing the problem in bind() function that generate error of the type: Address Already in Use. Here is one tip:
My problem was because the program ran and an address being used by the bind() and then the program generated errors and stopped/terminated. So the unlink() function at the end of the code had no chance to do its job and the address kept in use. So simplest way is at the beginning of the function unlink the processes you are going to bind later in the function.
This seems like so simple and I don't know if it is a good practice but it worked for my purpose.