Select system call don't 'select' readable descriptors

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C++

I want to create tcp server with select system call. When I connect to the server (I think I am at some level because when end server the client closes too) select gives me value of 0 readable descriptors? What is my mistake? This is the code:

int RelayServer::SendTcpPacket(uint8_t* payload, size_t len)
{
    int max_socket_so_far = 0;
    if(! server_is_set)
    {
        server_socket = SetupServer(port);
        server_is_set = true;
        cout<<"Relay server socket is set to: "<<server_socket<<endl;
    }

    conn_accepted = false;

        FD_ZERO(¤t_sockets);
        FD_SET(server_socket,¤t_sockets);
        
        if(FD_ISSET(server_socket, ¤t_sockets))
        {
            cout<<"Current socket is set with value of server_socket"<<endl;
        };

        max_socket_so_far = server_socket;

    while(! conn_accepted)
    {
        //beacause select is destructive
        ready_sockets = current_sockets;
        
        timeval tv;
        tv.tv_sec = 2;
        tv.tv_usec = 0;
        int numb_of_desc;
        numb_of_desc = select(max_socket_so_far,&ready_sockets, NULL, NULL, &tv);
        if(numb_of_desc < 0)
        {
            perror("select error");
        }
        cout<<"Number of descriptors ready to be read from is: "<<numb_of_desc<<endl;
        
        for(int i=0; i < max_socket_so_far;i++)
        {
            if(FD_ISSET(i, &ready_sockets))
            {
                if(i == server_socket){
                    //this is a new connection
                    cout<<"FOund server socket"<<endl;
                    client_socket = AcceptNewConnection(server_socket);
                    FD_SET(client_socket, ¤t_sockets);// add client socket to sockets which will be watching
                    if(client_socket > max_socket_so_far) {
                        max_socket_so_far = client_socket;
                    }  
                    conn_accepted = true;
                }
                else
                {
                    //do whatever we do with connections
                    int payload_ret =  HandleConnection(i,payload,len);
                    if(payload_ret != -1)
                    {
                        FD_CLR(i,¤t_sockets);
                        return payload_ret;
                    }
                    else
                    {
                        //close(client_socket);
                        //i = -1;
                        //continue;
                    }
                }
            }
        }
    }
    
    return 255;
}

What I have tried:

I tried to connect with ncat client to the server.
Also the client socket is in non-blocking mode if that matter somehow.