Parallel threads stopping each other

I want the following behavior in my application: while the application (server) is waiting for messages from another application (client), I want to be able to exit if it is too long with input from the user.

Therefore, I have to start two threads from the third:

• WaitForClientMessage
  
  
• WaitForUserInput
  
  

Using pthread

, I assumed I could call each thread and give them the id of the other, so if they run out, they override the other. But now I see that it won't work.

How to do it? I think it's easy because this behavior is often seen, but I don't know how to make it work.

EDIT Here is some generic code describing what I was imagining.

void main_thread( void)
{
    void * thread_rtn_val;

    /* Parallel threads */
    pthread_t thread_WaitForClientMessage;
    pthread_t thread_WaitForUserInput;

    /* Run Threads */
    pthread_create(&thread_WaitForClientMessage, NULL, run_window, (void *)thread_sdp);
    pthread_create(&thread_WaitForUserInput, NULL, run_client, (void *)arg_array);
}


void run_window( void)
{

    /* Refresh screen and watch for user input */
    for(...)
    {
        if(user press enter)
        {
            phtread_cancel(thread_WaitForClientMessage)
        }
    }
}


void run_client( void)
{
    /* Wait for client message */
    recv()...
    phtread_cancel(thread_WaitForUserInput)
}