// global
pthread_t serverTid;

// call the following after server's bind() and listen()
// Create a thread to handle keepalive miss count.
    if(pthread_create(&serverTid, NULL, serverHandleKeepalive, NULL) != 0)
    {
        perror("server pthread_create() failed");
        exit(EXIT_FAILURE);
    }

void* serverHandleKeepalive(void* arg)
{
    // printf("The keepalive handling thread started.\n");
    int reportCounter = 0;
    while(1)
    {
        int sessionIdx;
        for(sessionIdx = 1; sessionIdx < nclient + 1; sessionIdx++)
        {
            if(sessions[sessionIdx].socketFd <= 0)
            {
                continue;
            }

            if(sessions[sessionIdx].kalMissNum == 5)
            {
                // printf("loss of keepalive message: user '%s', fd = '%d', sessionIdx = '%d'\n",
                //     sessions[sessionIdx].username, pollfdArray[sessionIdx+1].fd, sessionIdx);
                // fflush(stdout);

                char tempTimeMsg[MAXCMDLEN];
                memset(sessions[sessionIdx].interactTime, 0, sizeof(sessions[sessionIdx].interactTime));
                getDateTime(sessions[sessionIdx].interactTime);
                strcpy(tempTimeMsg, sessions[sessionIdx].interactTime);
                memset(sessions[sessionIdx].interactTime, 0, sizeof(sessions[sessionIdx].interactTime));
                sprintf(sessions[sessionIdx].interactTime,
                    "'%s' [sockfd= %d]: loss of keepalive messages detected at %s, connection closed",
                    sessions[sessionIdx].username, sessions[sessionIdx].socketFd, tempTimeMsg);

                serverCloseChatSession(sessionIdx, ISEXIT);
            }
            else if(sessions[sessionIdx].kalMissNum < 5)
            {
                sessions[sessionIdx].kalMissNum += 1;
            }
        }

        sleep(KAL_interval);

        if(++reportCounter % 10 == 0)
        {
            printActivityReport();
        }
    }
}

// call the following when exiting the server
// Cancel the keepalive thread.
    pthread_cancel(serverTid);