#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>
 
#define max_ports 3
#define num_threads 6
 
sem_t portsemaphore;
 
 
void* open_port(void *thread_id) {
    int tid = *((int *)thread_id);
 
    printf("Thread %d: waiting to open port...\n", tid);
 
    sem_wait(&portsemaphore); 
    printf("Thread %d: PORT OPENED\n", tid);
 
    sleep(2); 
 
    printf("Thread %d: closing port.\n", tid);
    sem_post(&portsemaphore); 
 
    return NULL;
}
 
int main() {
    pthread_t threads[num_threads];
    int thread_ids[num_threads];
 
 
    sem_init(&portsemaphore, 0, max_ports);
 
    for(int i = 0; i < num_threads; i++) {
        thread_ids[i] = i + 1;
 
        pthread_create(&threads[i], NULL, open_port, &thread_ids[i]);
 
    }
 
 
    for(int i = 0; i < num_threads; i++) {
        pthread_join(threads[i], NULL);
    }
 
    sem_destroy(&portsemaphore);
    printf("All threads finished.\n");
    return 0;
}
 

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