How to use netlink socket to communicate with a kernel module?

I am trying to write a linux kernel module that communicates with user process using netlink. I am using netlink because the user program I want to communicate to communicates only using sockets and I cant change that to add ioctl() or anything.

Problem is that I cant figure out how to do that. I have googled but all examples I found are for old like this one and no longer valid for current kernel versions. I have also looked at this SO question but the sample here uses libnl for socket operations but I want to stick to standard socket functions (defined by sys/socket.h). So can some one plz guide me here to some tutorial or guide or some thing that can help me understand the interface and usage of netlink. I would highly appreciate a working example, nothing fancy, just a very basic example of how to establish a connection from a socket in user program to a socket in kernel and then send data from user process to kernel and receive back from kernel.

Also please do not tell me to look at kernel code. I am already doing it but it will take a lot of time and I dont have lot of it left.

Update: After lot of trial and error I have following code which sends message from user program to kernel but the message from kernel to user program i.e using netlink_unicast() is not working. Its not only not working, the call hangs the systems and then I have to restart the machine. Can same one plz take a look and tell me what wrong I am doing. The netlink_unicast() call is commented in the following code. It should be uncommented for kernel to user program message.

User Program

#include <sys/socket.h>
#include <linux/netlink.h>
#define NETLINK_USER 31
#define MAX_PAYLOAD 1024 /* maximum payload size*/

struct sockaddr_nl src_addr, dest_addr;
struct nlmsghdr *nlh = NULL;
struct iovec iov;
int sock_fd;
struct msghdr msg;

void main()
{

sock_fd=socket(PF_NETLINK, SOCK_RAW, NETLINK_USER);  
if(sock_fd<0)  
    return -1;  

memset(&src_addr, 0, sizeof(src_addr));  
src_addr.nl_family = AF_NETLINK;  
src_addr.nl_pid = getpid();  /* self pid */  
/* interested in group 1<<0 */  
bind(sock_fd, (struct sockaddr*)&src_addr,  
  sizeof(src_addr));  

memset(&dest_addr, 0, sizeof(dest_addr));  
memset(&dest_addr, 0, sizeof(dest_addr));  
dest_addr.nl_family = AF_NETLINK;  
dest_addr.nl_pid = 0;   /* For Linux Kernel */  
dest_addr.nl_groups = 0; /* unicast */  

nlh = (struct nlmsghdr *)malloc(  
                      NLMSG_SPACE(MAX_PAYLOAD));  
memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD));  
nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);  
nlh->nlmsg_pid = getpid();  
nlh->nlmsg_flags = 0;  

strcpy(NLMSG_DATA(nlh), "Hello");  

iov.iov_base = (void *)nlh;  
iov.iov_len = nlh->nlmsg_len;  
msg.msg_name = (void *)&dest_addr;  
msg.msg_namelen = sizeof(dest_addr);  
msg.msg_iov = &iov;  
msg.msg_iovlen = 1;  

printf("Sending message to kernel\n");  
sendmsg(sock_fd,&msg,0);  
printf("Waiting for message from kernel\n");  

/* Read message from kernel */  
recvmsg(sock_fd, &msg, 0);  
printf(" Received message payload: %s\n",  
    NLMSG_DATA(nlh));  
close(sock_fd);

}

Kernel Code

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <net/sock.h>
#include <linux/socket.h>
#include <linux/net.h>
#include <asm/types.h>
#include <linux/netlink.h>
#include <linux/skbuff.h>

#define NETLINK_USER 31

struct sock *nl_sk = NULL;

static void hello_nl_recv_msg(struct sk_buff *skb)
{

    struct nlmsghdr *nlh;  
    int pid;  

    printk(KERN_INFO "Entering: %s\n", __FUNCTION__);  

    nlh=(struct nlmsghdr*)skb->data;  
    printk(KERN_INFO "Netlink received msg payload: %s\n",
        (char*)NLMSG_DATA(nlh));  
    pid = nlh->nlmsg_pid; /*pid of sending process */  
    NETLINK_CB(skb).dst_group = 0; /* not in mcast group */  
    NETLINK_CB(skb).pid = 0;      /* from kernel */  
    //NETLINK_CB(skb).groups = 0; /* not in mcast group */  
    //NETLINK_CB(skb).dst_pid = pid;  
    printk("About to send msg bak:\n");  
    //netlink_unicast(nl_sk,skb,pid,MSG_DONTWAIT);

}

static int __init hello_init(void)
{

    printk("Entering: %s\n",__FUNCTION__);  
    nl_sk=netlink_kernel_create(&init_net, NETLINK_USER, 0,
           hello_nl_recv_msg, NULL, THIS_MODULE);  
    if(!nl_sk)  
    {   
            printk(KERN_ALERT "Error creating socket.\n");  
            return -10;  
    }  
    return 0;

}

static void __exit hello_exit(void)
{

    printk(KERN_INFO "exiting hello module\n");  
    netlink_kernel_release(nl_sk);

}

module_init(hello_init);
module_exit(hello_exit);

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