What is the length of of the queue for pending connections in this program?

#include<stdio.h>
#include<sys/types.h>
#include<sys/un.h>
#include<sys/socket.h>
 
int main()
{
    struct sockaddr_un add_server;
    int fd_server;
    fd_server = socket(AF_UNIX,SOCK_STREAM,0);
    if(fd_server == -1)
        perror("socket");
    add_server.sun_family = AF_UNIX;
    strcpy(add_server.sun_path,"server_sock2");
    if( bind(fd_server,(struct sockaddr*)&add_server,sizeof(add_server)) != 0)
        perror("bind");
    if( listen(fd_server,3) != 0)
        perror("listen");
    return 0;
}