server.cpp

// Header File and some macros which helped me in my code

#include <unistd.h>
#include <stdio.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <string.h>
#include <pthread.h>
#include <thread>
#include <arpa/inet.h>
#include <bits/stdc++.h>
#define all(v) (v).begin(), (v).end()
#define lp(i, n) for (int i = 0; i < (n) ; ++i)
#define lpp(i, n) for (int i = 1; i <= (n) ; ++i)
#define lpi(i, j, n)    for(int i=(j);i<(int)(n);++i)
#define lpd(i, j, n)    for(int i=(j);i>=(int)(n);--i)
#define sz(v) (int)(v).size()
#define clr(v, d)       memset(v, d, sizeof(v))
#define mod 100000007
using namespace std;
#define PORT 8000


// DataStucture for Sheard Memoreis
typedef struct {
    // to store the contant as string
    string memo ;
    // to know client make lock
    int lockedBy ;
    // dynamic memory to store clients sheards this memory
    set<int> sheardBy;
} memory ;
// dynamic array [ key - > value ] to store the memores
map<int, memory>memories ;



// Function handle The request and make new sesstion with new client
// Or Old client
void requestHandler(void* data) {
    int new_socket = *((int*)data) ;
    char buffer[1024] = {0};
    // some messages to make acknowledge for the request is accepted or not
    char success[] = "1:";
    char failed[] = "0:";

    // Get User Id And Sheard Memory Id ..
    read( new_socket , buffer, 1024);
    int id = atoi(buffer);
    int  i  ;
    for ( i = 0; i < (int)strlen(buffer); ++i) {
        if (buffer[i] == ':') {
            i++;
            break;
        }
    }

    int memoId = atoi(buffer + i);
    cout << id << " ID " << memoId << " request type " << endl;
    send(new_socket , success , strlen(success) , 0 );

    /*
     * The client sends the shared memory key (int) to server, if memory already exist
    the client will be added to that memory list of clients, otherwise the memory is
    allocated first
     * */
    if (memories.count(memoId) == 0) { // Memory Does Not Exist
        memory a  ;
        a.memo = "Empty";
        a.lockedBy = -1 ;
        a.sheardBy.insert(id);
        memories[memoId] = a;
    } else {
        memories[memoId].sheardBy.insert(id) ;
    }

    //Get Msg Type { 1 , 2  ,3,  4 ,5 , 6  } .
    read( new_socket , buffer, 1024);
    int msgType = atoi(buffer);
    cout << "msg Type is " << msgType << endl;
    //send(new_socket , success , strlen(success) , 0 );

    if (msgType == 1) { // LOCK REQUEST

        if (memories[memoId].lockedBy == -1 || memories[memoId].lockedBy == id) {
            cout << "Locked by " << id << endl;
            memories[memoId].lockedBy = id ;
            send(new_socket , success , strlen(success) , 0 );
        } else {
			while(memories[memoId].lockedBy != -1){
				;
			}
			memories[memoId].lockedBy= id ;
            cout << "Locked by " << id << endl;
            send(new_socket , success , strlen(success) , 0 );
        }
        return ;
    } else if (msgType == 2) {
        if (memories[memoId].lockedBy == id) {
            cout << "Success UNLOCKED " << id << endl;
            memories[memoId].lockedBy = -1 ;
            send(new_socket , success , strlen(success) , 0 );
        } else {
            cout << "Fail Unlocked " << id << endl;
            send(new_socket , failed , strlen(failed) , 0 );
        }
        return ;

    } else if (msgType == 3) { // Read

        if (memories[memoId].lockedBy == id) {
            char res[1000] ;
            lp(i, memories[memoId].memo.size()) {res[i] = memories[memoId].memo[i]; res[i + 1] = '\0';}
            send(new_socket , res , strlen(res) , 0 );
        } else {
            cout << "Fail Read by " << id << endl;
            send(new_socket , failed , strlen(failed) , 0 );
        }
        return ;

    } else if (msgType == 4) { // Write

        if (memories[memoId].lockedBy == id) {
            send(new_socket , success , strlen(success) , 0 );
            //read( new_socket , buffer, 1024);
            char res[1024] ;
            read( new_socket , res, 1024);
            string s(res);
            memories[memoId].memo = s;
            cout << s << endl ;
            send(new_socket , success , strlen(success) , 0 );
        } else {
            cout << "Fail Write by " << id << endl;
            send(new_socket , failed , strlen(failed) , 0 );
        }
        return ;
    } else if (msgType == 5) {
        // creat new Memory
        if (memories.count(memoId) == 0) { // Memory Does Not Exist
            memory a  ;
            a.memo = "Empty";
            a.lockedBy = -1 ;
            a.sheardBy.insert(id);
            memories[memoId] = a;
        } else {
            memories[memoId].sheardBy.insert(id) ;
        }


    } else if (msgType == 6) { // Remove client id from memory clients list
        memories[memoId].sheardBy.erase(id);
        if (memories[memoId].sheardBy.size() == 0) {
            memories.erase(memoId);
        }
         send(new_socket , success , strlen(success) , 0 );
    }





}

int main()
{
    int server_fd, new_socket ;
    struct sockaddr_in address, peer_addr;
    int opt = 1;
    int addrlen = sizeof(address);

    // Creating socket file descriptor
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0)
    {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // Forcefully attaching socket to the port 8080
    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt)))
    {
        perror("setsockopt");
        exit(EXIT_FAILURE);
    }
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons( PORT );

    // Forcefully attaching socket to the port 8080
    if (bind(server_fd, (struct sockaddr *)&address,
             sizeof(address)) < 0)
    {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }
    if (listen(server_fd, 3) < 0)

    {
        perror("listen");
        exit(EXIT_FAILURE);
    }

    while (1) {
        if ((new_socket = accept(server_fd, (struct sockaddr *)&peer_addr,
                                 (socklen_t*)&addrlen)) < 0)
        {
            perror("accept");
            exit(EXIT_FAILURE);
        }
        // Get IP Address for client
        //
        pthread_t  p_thread;
        pthread_create(&p_thread, NULL, reinterpret_cast<void *(*)(void *)>(requestHandler), (void*)&new_socket);
    }
    return 0;
}