Client Server programming with threads

Question

I am working on client server code where a client has two threads running; I want both these threads to run continuously for 60 sec. However, I am facing two problems.

Firstly, when I am running the for loop in main(), the retail_thread() is generating the same number it should have generated random number instead, as bulk_thread() is generating. Secondly, I am not able to get the idea of running the for loop exactly 60 sec.

As it is a homework problem I will really appreciate any hints or assistance if not the exact solution. Please ignore typos if any.

int main(int argc, char *argv[]) {

    int pt,i;
    pthread_t thread;
    /* n a very large number */
    /* run below code for 60 seconds */

    for(i=0;i<n;i++)
    {
        pt = pthread_create(&thread, NULL, retail_thread, (void*) NULL);
        bulk_thread(NULL);
    }
}

void* retail_thread(void* ){
    srand(time(NULL));                       
    int order_size = rand()%20 + 1;         
    printf("in retail \n ");
    sendtoserver_R(RETAIL_PORT,order_size);
    int wait_time = 100 + (5*order_size);
    printf("Retail thread order = %d and execution fully completed \n\n",order_size);
}

void* bulk_thread(void* ){
    srand(time(NULL));                      
    int order_size = rand()%90 + 10;        
    printf("in bulk \n");
    int wait_time = 100 + (5*order_size);
    sendtoserver_B(BULK_PORT,order_size);

    printf("Bulk thread order = %d and execution fully completed \n\n",order_size);
}

sendtoserver() is just for creating socket and sending data to server.

What exactly do you want to happen after 60s? Beware there might several threads be running at that moment, doing different things. — alk, Mar 16 '13 at 10:49
@alk I just want to count the number of orders server has received — Vbp, Mar 16 '13 at 10:51
"*... where a client has two threads running ...*" your code could easily produces more then two threads running at a time. — alk, Mar 16 '13 at 10:54
What the server received you should better count on the server side. Did you mean to count the number of orders **sent to** the server? — alk, Mar 16 '13 at 10:57
@alk Yes I mean the numbers of order sent to server that I am handling in a separate function I appreciate your time and assistance actually counting is just a small part of the problem, I will comment back if i need any help. Thank you!! — Vbp, Mar 16 '13 at 11:03

Leo Chapiro · Accepted Answer · 2013-03-16T10:48:34.080

3

Well, I think the first problem is:

// Seed the RNG once, at the start of the program
srand(time(NULL));  

void* retail_thread(void* ){
    //srand(time(NULL));                       
    int order_size = rand()%20 + 1;         
    printf("in retail \n ");
    sendtoserver_R(RETAIL_PORT,order_size);
    int wait_time = 100 + (5*order_size);
    printf("Retail thread order = %d and execution fully completed \n\n",order_size);
  }

[EDITED] To run a thread 60 sec you can try this:

time_t end = time(NULL) + 60;
while (time(NULL) <= end)
{
    … // do something
}

edited Mar 16 '13 at 10:48

answered Mar 16 '13 at 10:30

Leo Chapiro

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please correct me if I am wrong, But rand() is not thread-safe if I seed it only once I may get undefined behavior or segfault. – Vbp Mar 16 '13 at 10:33
Take a look at this answer please, it's exactly your problem: http://stackoverflow.com/a/6161352/1758762 – Leo Chapiro Mar 16 '13 at 10:37
Thank you so much, I did seed once in main() and now retail_thread() is generating random numbers could you please assist me with the second problem where in I have to run the "for loop" exactly 60 seconds – Vbp Mar 16 '13 at 10:42
I accepted your answer Thank you! so much I was trying so hard figuring out where I am going wrong. Appreciate your time!! – Vbp Mar 16 '13 at 10:58
This might be nitpicking, depending on the use case, but as the OP mentions *exactly 60s* your proposal does not really work, as it will continue "*... doing something ...* after the 60th second. Even if you change `<= end` to be `< end` this would not help as the loop might break before 60s have elapsed. So as the use case is not 60.0s a possible way to go would be to use a clock providing a higher resolution than `time()` does. – alk Mar 16 '13 at 11:03

Client Server programming with threads

1 Answers1